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Friday, January 11, 2008
Thursday, January 3, 2008
PROCESSING DEVICE
This topic includes the following sections:
• How Computers Represent Data
• How Computers Process Data
• Factors Affecting Processing Speed
How Computers Represent Data:
• Binary Numbers
• The Binary Number System
• Bits and Bytes
• Text Codes
How Computers Represent Data– Binary Numbers
• Computer processing is performed by transistors, which are switches with only two possible states: on and off.
• All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.
• If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
How Computers Represent Data - Bits and Bytes
• A single unit of data is called a bit, having a value of 1 or 0.
• Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.
• Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.
• With one byte, the computer can represent one of 256 different symbols or characters.
How Computers Represent Data - Text Codes
• A text code is a system that uses binary numbers (1s and 0s) to represent characters understood by humans (letters and numerals).
• An early text code system, called EBCDIC (Extended Binary Coded Decimal Interchange Code), uses eight-bit codes, but is used primarily in older mainframe systems.
• In the most common text-code set, ASCII (American Standard Code for Information Interchange), each character consists of eight bits (one byte) of data. It specifies characters for values from 0 to 127. Extended ASCII specifies characters for values from 128 to 255. ASCII is used in nearly all personal computers.
• In the Unicode text-code set, each character consists of 32 bits (four bytes) of data. Mostly all characters used in word like Chinese, Korean and Japanese and mathematical symbols can be represented
How Computers Process Data
• Where Processing Occurs
• The Control Unit
• The Arithmetic Logic Unit
• Machine Cycles
• The Role of Memory in Processing
• Types of RAM
How Computers Process Data – Where Processing Occurs
• Processing takes place in the PC's central processing unit (CPU).
• The system's memory also plays a crucial role in processing data.
• Both the CPU and memory are attached to the system's motherboard, which connects all the computer's devices together, enabling them to communicate.
How Computers Process Data –The Control Unit
• The two main parts of a CPU are the control unit and the arithmetic logic unit (ALU)
• The control unit directs the flow of data through the CPU, and to and from other devices.
• The control unit stores the CPU's instruction set, which contains the list of instructions for all the tasks the CPU can perform.
• Each instruction is expressed in microcode a series of basic directions that tell the CPU how to execute more complex operations.
How Computers Process Data –The Arithmetic Logic Unit
• The actual manipulation of data takes place in the ALU.
• The ALU can perform arithmetic and logic operations.
• The ALU is connected to a set of registers—high speed memory locations built directly in to the CPU that are used to hold data and program instructions currently being processed.
How Computers Process Data –Machine Cycles
• To execute each instruction, the CPU follows a series of steps-called a machine cycle. The machine cycle includes two smaller cycles.
1. Instruction cycle
Fetching: Before the CPU can execute an instruction, the control unit must retrieve a command or data from memory
Decoding: Before execution, CU break down the command into instruction that corresponds to those in the instruction set.
2. Execution cycle
Executing: When the command is executed, the CPU carries out the instruction by converting them into micro codes.
Storing: CPU may be required to store the results of an instruction in memory
• CPU performance is measured in MIPS and BIPS.
• By using a technique called pipelining, many CPUs can process more than one instruction at a time.
• Multitasking by hyper threading (Pipelining).
The Role of Memory
• Nonvolatile memory: Permanent. ROM
• PROM chip ->Chip that cannot be changed .Used in printer and hard drives.
• ROM contains a set of start up instruction->BIOS.
• BIOS contain POST to ensure that the system is functioning properly and all expected hardware devices are present.
• Flash memory: Special type of nonvolatile memory used in portable digital devices like digital camera, portable MP3 player, USB.
• Volatile memory: Non permanent. RAM
Single in line memory module, Dual in line memory module
There are two basic types of RAM: static and dynamic
• Dynamic RAM (DRAM) chips must be recharged with electricity very frequently, or they will lose their contents. One transistor per bit, slower, cheaper, larger capacity
• Static RAM (SRAM) does not need to be recharged as often as DRAM, and can hold its contents longer.
To store and retrieve data CPU uses Memory address a number that indicates a location on the memory chip.
Factors Affecting Processing Speed
• Registers
• RAM
• The System Clock
• The Bus
• Cache Memory
Factors Affecting Processing Speed – Registers
• The CPU contains a number of small memory areas, called registers, which store data and instructions while the CPU processes them.
• The size of the registers (also called word size) determines the amount of data with which the computer can work at a one time.
• Today, most PCs have 32-bit registers; mean the CPU can process four bytes of data at one time. Register sizes are rapidly growing to 64 bits.
Factors Affecting Processing Speed – RAM
• The amount of RAM in a PC has a direct affect on the system's speed.
• The more RAM a PC has, the more program instructions and data can be held in memory, which is faster than storage on disk.
• If a PC does not have enough memory to run a program, it must move data between RAM and the hard disk frequently. This process, called swapping, can greatly slow a PC's performance.
• Process of swapping unused content of RAM to hard disk is called Virtual memory
Factors Affecting Processing Speed -The System Clock
• A single "tick" of the clock is the time required to turn a transistor off and back on. This is called a clock cycle.
• Clock cycles are measured in Hertz (Hz), a measure of cycles per second. If a computer has a clock speed of 300 MHz, then its system clock "ticks" 300 million times every second.
• The faster a PC's clock runs, the more instructions the PC can execute each second.
Factors Affecting Processing Speed -The Bus
• A bus is group of parallel wires. Each wire can transfer one bit at a time.
• Data bus is an electrical path between the components of a computer. Data and instructions travel along this bus.
• The data bus' width determines how many bits can be transmitted between the CPU and other devices.
• The address bus runs only between the CPU and RAM, and carries nothing but memory addresses for the CPU to use.
• Peripheral devices are connected to the CPU by an expansion bus.
Factors Affecting Processing Speed -Cache Memory
• Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.
• Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.
• CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache. Cache present resident as well as external to CPU is called Level-3(L3) cache.
• The amount of cache memory has a tremendous impact on the computer's speed.
Processors:
X= (A+B) * (C+D)
• RISC Processor- Reduced instruction set computing
Instruction set is small and the instruction is simple.
Y=A+B
Z=C+D
X=Y*Z
• CISC Processor–Complex instruction set computing
Instruction set is large and the instruction is complex.
X= (A+B) * (C+D)
MEMORY DEVICES
Types of ROM:
Mask ROM:
• It is permanently programmed during the manufacturing process according to the customer application.
• Once the memory is programmed it cannot be changed
PROM:
• In order to provide same flexibility in the application of ROM Programmable ROM (PROM) is introduced.
• It can be programmed electrically by the user but cannot be reprogrammed
• It is used in the control of electrical equipment such as washing machine and electric arm.
EPROM (Erasable Programmable ROM):
• A PROM device that can be erased and reprogrammed is called erasable PROM.
• To program a different data, all cells in the EPROM must be erased. This is done by illuminating the cells by a strong UV light having a wavelength typically 253.7 nm for about 20 minutes.
• It is provided with a transparent quartz window on the top of the chip to allow the UV rays for erasing the data.
• The window should be covered with an opaque sticker to protect the memory from unwanted exposure to UV rays from sunlight and fluorescent lamps.
• The new data can be stored by programming electrically thus EPROM is UV erasable and electrically programmable.
Disadvantages of EPROM:
• Changes in the selected memory locations cannot be made in the reprogramming
• The chip on the whole should be erased
• The EPROM IC must be removed from the circuit and then the memory is erased by exposing to UV light through a window. Thus it takes nearly 30 minutes.
EEPROM (Electrically Erasable PROM):
• It overcomes the disadvantages of ERPOM. It can be erased and programmed by the application of control electricity pulses to the IC in the circuit and thereby changes can be made in the desired portion of IC.
• EEPROM is nonvolatile like EPROM but does not require UV light for erasing.
• EEPROM is a low power semiconductor device and it occupies less space.
• It has the advantage of program flexibility, small size and semiconductor memory (low voltage and no mechanical parts).
Types of RAM:
Static RAM:
• It essentially contain an array of flip-flop one of each bit. Data written into flip-flop remains stored as long as the power is maintained.
• Memory capacity of static RAM varies from 64 bits to 1 Mega bits.
DRAM (Dynamic RAM):
• It is the lowest cost, highest density RAM available.
• Computers use DRAM for main memory storage with the memory size ranging from 16 Mega bytes to 256 Mega bytes.
• It stores its binary information in the form of electric charges on capacitors. Hence it must be recharged or refreshed 1000 of times every second in order to retain these stored charges.
• It uses integrated mass capacitor as basic memory cell instead of flip-flop.
Pseudo static RAM:
• It is basically a dynamic RAM. It has built in refresh logic. Hence no external refreshing circuit is required and there by Pseudo static RAM can be used as a static RAM device.
• When this device is performing internal refresh it cannot be accessed for read or write operation
• The capacity is 64 Kbits and more.
INPUT DEVICES
This Topic includes the following sections:
The Keyboard
The Mouse
Variants of the Mouse
The Keyboard
• The Standard Keyboard Layout
• Ergonomic Keyboards
• How a Keyboard Works
•
The Keyboard - Standard Keyboard Layout
• A standard computer keyboard has about 100 keys.
• Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters.
The Keyboard - Standard Keyboard Layout
Most keyboards have keys arranged in five groups:
• Alphanumeric keys
• Numeric keypad
• Function keys
• Modifier keys
• Cursor-movement keys
The Keyboard - Ergonomic Keyboards
• Ergonomics->Study of Physical relationship between people and their tools.
• Long periods of keyboard use can cause injuries.
• An ergonomically correct keyboard can help you to avoid repetitive stress (strain) injuries (RSI).
• You also can avoid injuries by adopting correct keyboarding practices.
The Keyboard - How a Keyboard Works
When you press a key:
• The keyboard controller detects the keystroke.
• The controller places a scan code in the keyboard buffer, indicating which key was pressed.
• The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke.
The Mouse - What is a Mouse?
• The mouse is a pointing device. You use it to move a graphical pointer on the screen.
• The mouse can be used to issue commands, draw, and perform other types of input tasks.
Variants of the Mouse
• Trackballs
• Track pads
• Integrated Pointed Devices
Types of Mouse
• 1.Mechanical Mouse
• 2.Optical Mouse (Non mechanical)
Mouse Function (Mechanical)
Mouse movesà Mouse ball spins the rollerà Roller gives information to the system softwareà System software controls the pointer
Mouse Function (Optical)
Mouse emits a beam of lightà From the Reflected light distance, direction and speed of pointer is evaluatedà System software controls the pointer.
The Mouse - Mouse Techniques:
Using the mouse involves five techniques:
Pointing; Move the mouse to move the on-screen pointer.
Clicking; Press and release the left mouse button once.
Double-clicking; Press and release the left mouse button twice.
Dragging; Hold down the left mouse button as you move the pointer.
Right-clicking; Press and release the right mouse button.
Variants of the Mouse - Trackballs
• A trackball is like a mouse turned upside-down & needs less working space.
• Use your thumb to move the exposed ball and your fingers to press the buttons.
Track pads:
• A track pad is a touch-sensitive pad that provides the same functionality as a mouse.
• To use a track pad, you glide your finger across its surface.
• Track pads provide a set of buttons that function like mouse buttons.
Integrated Pointing Devices
• An integrated pointing device is a small joystick built into the keyboard between G and H.
• To use an integrated pointing device, you move the joystick.
• These devices provide a set of buttons that function like mouse buttons
Alternative Input Devices – Devices for the Hand
• Pens
• Touch Screens
• Game Controllers
•
Devices for the Hand – Pens
• With a pen-based system, you use an electronic pen called as stylus to write on the screen and choose commands.
• Pens are common input devices for handheld computers, like personal digital assistants (PDAs) and tablet PC for collecting database
• Pens are handy for making notes or selecting commands, not for inputting a lot of text.
Devices for the Hand - Touch Screens
• Touch-screen systems accept input directly through the monitor.
• Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse.
• Touch-screen systems are useful for selecting options from menus.
• They are useful for ATM, information centre like railways, departmental stores etc.
Devices for the Hand - Game Controllers
• Game controller is an input device which accepts I/p from the user, process it, and produce o/p in the form of graphics and sound
• The two primary types of game controllers are joysticks and game pads.
• Game pads usually provide controls for each hand. They are flexible and used to control games
• Joysticks are popular for flight simulator and driving games. Some type includes steering wheel, gearshifts and foot pedals.
Alternative Input Devices –Optical Input Devices
• Bar Code Readers
• Image Scanners and OCR (Optical Character Recognition)
Optical Input Devices - Bar Code Readers
• Bar code readers can read bar codes—patterns of printed bars to identify the product.
• The reader emits light, which reflects off the bar code.
• A light sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.
• They tell the reader whether the barcode has been read right side up or upside down. Then it converts the individual bar patterns into corresponding code. Then the reader feeds the data into the computer.
• Flatbed bar code readers are commonly found in library, supermarkets. Courier services often use handheld readers.
Optical Input Devices: Image Scanners and OCR
• Image scanner converts any printed image into electronic form by shining light onto the image and sensing the intensity of light reflection at every point.
• Thus they digitize printed images for storage and manipulation in a computer.
• Color scanners use filters to separate the components of color into the primary additive color (RGB)
• After scanning, when it is a photo we can use photo shop application to change the properties of picture like adjusting contrast, changing color etc.
• Scanners come in a range of size from hand held model to flat bed scanners that sit on desktop.
• Hand held scanners or portable but require multiple passes to scan a single page because they are not wide as paper.
• Flat bed scanners offered high quality reproduction since it can scan a page in single pass (Xerox m/c).
• Some medium sized scanners are also available (FAX m/c).
OCR (Optical Character Recognisation):
• When it is a text document we can use Optical character recognition (OCR) software to translate scanned text into editable electronic documents.
• Image is first stored as bit map. A bit map is grid of dots; each dot is represented by one or more bits.
• OCR translates the array of dots into letters and numbers.
• For that, it looks at each character and tries to match the character with its own assumption. OCR extremely complex and not 100% accurate.
• It is used to convert the fax into editable document.
Alternative Input Devices – Audio-Visual (Multimedia) Input Devices
• Audio input Microphones and Speech Recognition
• Video Input PC video camera, Digital camera
Microphones and Speech Recognition
• Microphones can accept auditory input. A microphone requires a sound card in the PC.
• A sound card is a special device which translate analog sound signal from the microphone into digital codes the computer can store and process .This process is called digitizing. Vice-versa can also be done by sound card.
• By this we can record our voice and store it as file in computer. We can use it in presentations; webpage’s or email it to others.
• With speech recognition software (voice recognition), you can use your microphone to dictate text, navigate programs, and choose commands.
• SRS takes the smallest individual sound in a language called phonemes, and translate them into text.
• Some problem occurs are
1. Differentiating sound for e.g.: during the process of two and too.
2. To isolate background noise.
3. Need of pause between words.
• Newer software overcomes these problems by training with speech patterns and pronunciation.
• Other types of audio I/p are CD, tape player, radio…
MIDI-Musical Instrument Digital interface
A MIDI port or adapter is used to connect the musical instruments to computer.
Video Input
• Applications like video conferencing and video chat needs video files to be communicated between computers.
• PC video cameras digitize full-motion images and can transmit them in n/w. eg:webcam
• It breaks images into pixels and each pixel’s color and characteristics are stored as digital code.
• Video capture card is used to connect video devices to PC.
• Digital cameras are portable, handheld device that capture still images.
• Difference between normal film camera and digital camera.
• Video images may be compressed to use less memory and storage space for passing in network.
PRINTING DEVICES
Overview of Printers - Categorizing Printers
• Printers fall into two categories: Impact printers: use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper.Non-impact printers: use different methods to place ink (or another substance) on the page.
Dot Matrix Printers -How Do Dot Matrix Printers Work?
• Dot matrix printers are a common type of impact printer.
• A dot matrix printer's print head contains a cluster of pins. The printer can push the pins out to form patterns in rapid sequence.
• The pins press an inked ribbon against the paper, creating an image.
Dot Matrix Printers - Performance
• Lower-resolution dot matrix printers use nine pins. Higher-resolution models have 24 pins.
• Speed is measured in characters per second (cps). Some dot matrix printers print 500 cps.
Ink Jet Printers –How Do Ink Jet Printers Work?
• Ink jet printers are an example of non-impact printers.
• The printer sprays tiny droplets of ink onto the paper.
• Ink jet printers are available for color and black-and-white printing.
Ink Jet Printers - Performance
• Ink jet printers offer speeds of (2 – 4 pages per minute ppm) and resolution (300 – 600 dots per inch dpi), comparable to low-end laser printers. Ink jet printers are inexpensive and have low operating costs.
Laser Printers –How Do Laser Printers Work?
Laser printers are non-impact printers. They use heat and pressure to bond particles of toner to paper. Laser printers are available for color and black and white printing.
Laser Printers - Performance
• Laser printers provide resolutions from 300 – 1200 dpi and higher.
• Black-and-white laser printers usually produce 4 – 16 ppm.
• Laser printers produce higher-quality print than ink jet printers, but are more expensive.
Overview of Printers - Evaluating Printers
When evaluating printers, consider four criteria
• Image quality – Measured in dots per inch (dpi). Most printers produce 300 – 600 dpi.
• Speed – Measured in pages per minute (ppm) or characters per second (cps)
• Initial cost – Consumer printers cost $250 or less, but professional printers can cost thousands of dollars.
• Cost of operation – This refers to the cost of supplies used by the printer.
Photo printers
Used to print images that can be created by using Digital camera or scanner.
Thermal – Wax printer
• Presentation Graphics and handouts.
• Bold colors with heavy color requirement, posters or book covers.
• Ribbon coated with panels of colored Wax that melts and adheres to plain paper as colored dots when passed over a focused heat source.
Dye – Sublimation printers
• Get Realistic quality and color for photo images- Desktop publishers, artist.
• Ribbon containing panels of color is moved across a focused heat source.
• Capable of subtle temperature variations.
• The heated dyes evaporated from the ribbon and diffuse on specially coated paper.
• The variation to the color is related to the intensity of the color applied.
• Create sharp images. Slow.
Plotters
• Same like printer except that it is used to print large format images – construction drawings created by an architect.
• Early plotter: Mechanical device contains robotic arm used to draw images on paper.
• Table plotter: Two robotic arms contain colored ink pens.
• Two arms operating at right angles as they draw on a stationary paper.
• Large and complex table plotters are notoriously slow.
• Large complicated drawings can take several hours to print
Roller plotter – Drum plotter
• one drawing arm but moves the paper.
• The drawing arm moves side to side as the paper is rolled back and forth.
• Draw perfect circles and other geometric shapes.
• Mechanical plotters replaced by Thermal, electro static, ink jet plotters and dye – sub printers.
• These devices can also produces large size drawings are faster and cheaper than mechanical plotters
STORAGE DEVICES
This lesson includes the following sections:
• Categorizing Storage Devices
• Magnetic Storage Devices
• Optical Storage Devices
Categorizing Storage Devices
• Storage devices hold data, even when the computer is turned off.
• The physical material that actually holds data is called storage medium. The surface of a floppy disk is storage medium.
• The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.
• The two primary storage technologies are magnetic and optical.
The primary types of magnetic storage are:
• Diskettes (floppy disks)
• Hard disks
• High-capacity floppy disks
• Disk cartridges
• Magnetic tape
The primary types of optical storage are:
• Compact Disk Read-Only Memory (CD-ROM)
• Digital Video Disk Read-Only Memory (DVD-ROM)
• CD-Recordable (CD-R)
• CD-Rewritable (CD-RW)
• PhotoCD
Magnetic Storage Devices
• How Magnetic Storage Works
• Formatting
• Disk Areas
• Diskettes
• Hard Disks
• Disk Capacities
• Other Magnetic Storage Devices
Magnetic Storage Devices- How Magnetic Storage Works
• A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions.
• Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.
• A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.
Magnetic Storage Devices – Formatting
• Before a magnetic disk can be used, it must be formatted—a process that maps the disk's surface and determines how data will be stored.
• During formatting, the drive creates circular tracks around the disk's surface, and then divides each track into sectors.
• The OS (Operating System) organizes sectors into groups, called clusters, and then tracks each file's location according to the clusters it occupies.
Magnetic Storage Devices - Disk Areas
When a disk is formatted, the OS creates four areas on its surface:
• Boot sector – stores the master boot record, a small program that runs when you first start (boot) the computer
• File allocation table (FAT) – a log that records each file's location and each sector's status
• Root folder – enables the user to store data on the disk in a logical way
• Data area – the portion of the disk that actually holds data.
Magnetic Storage Devices – Diskettes
• Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies).
• Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium.
• Diskettes come in two sizes: 5.25-inch and 3.5-inch.
Magnetic Storage Devices - Hard Disks
• Hard disks use multiple platters, stacked on a spindle. Each platter has two read/write heads, one for each side.
• Hard disks use higher-quality media and a faster rotational speed than diskettes.
• Removable hard disks combine high capacity with the convenience of diskettes.
Magnetic Storage Devices - Disk Capacities
• Diskettes are available in different capacities, but the most common store 1.44 MB.
• Hard disks store large amounts of data. New PCs feature hard disks with capacities of 10 GB and higher.
Magnetic Storage Devices - Other Magnetic Storage Devices
• High-capacity floppy disks offer capacities up to 250 MB and the portability of standard floppy disks.
• Disk cartridges are like small removable hard disks, and can store up to 2 GB.
• Magnetic tape systems offer very slow data access, but provide large capacities and low cost.
Optical Storage Devices
• How Optical Storage Works
• CD-ROM
• CD-ROM Speeds and Uses
• DVD-ROM
• Other Optical Storage Devices
Optical Storage Devices – How Optical Storage Works
• An optical disk is high-capacity storage medium. An optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.
• When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).
Optical Storage Devices – CD-ROM
• In PCs, the most commonly used optical storage technology is called
Compact Disk Read-Only Memory (CD-ROM).
• A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio.
• Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.
Optical Storage Devices – CD-ROM Speeds and Uses
• Early CD-ROM drives were called single speed, and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 – 15 MBps).
• CD-ROM drives now can transfer data at speeds of up to 7800 KBps. Data transfer speeds are getting faster.
• CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions.
Optical Storage Devices - DVD-ROM
• A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.
• Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.
• DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.
Optical Storage Devices - Other Optical Storage Devices
• A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk.
• A CD-Rewritable (CD-RW) drive lets you record a CD, and then write new data over the already recorded data.
• PhotoCD technology is used to store digital photographs.
SYSTEM SOFTWARE
System ↔ System ↔ Application ↔ Computer
User Software Software System
System Software: It is a collection of programs designed to operate, control and extend processing capabilities of computer and which makes the operation of a computer system more effective and efficient.It comprises of1.Operating system2.Device driver3.System utility4.Language translators
Operating System:
A collection of programs used to control and coordinate the computer system. It manages functions performed by hardware, I/O devices, CPU, Secondary storage devices, communication and n/w equipment.
Functions of operating system:
• Memory management: It allocates and deallocates the memory of user program.
• Process management: Manages program in execution. It schedules CPU and shares the CPU among many processes.
• File management: Manages organization, naming, storing, retrieving, sharing and protection of files.
• Device management: Controls all the I/O devices and provides flexible and easy interface.
• Security management: Protects the system resources and information against destruction and unauthorized access.
• User Interface: It allows the user to give inst. And retrieve info. From the system.
Device Driver
• Special programs to extend the ability of OS in order to support I/O devices such as keyboard, mouse, monitor, printer…
• It contains all possible device dependent codes.
• It accepts request from device, translate it into commands for the appropriate device controller.
Computer System ↔ Device Driver ↔ I/O Device
System utility:
• Small program having specific tasks to perform which helps the user maintenance of system
Functions of system utility:
1. File management2. Backup3. Data recovery4. Virus protection5. Disk management6. Firewall7. Disk cleanup
Language Translator:
Tool that translates a programming language to m/c language which is understandable by a computer.
Categories of translators:
• Compiler: Converts high level language to m/c level language.or it converts source code (program) into object code (binary form) as a whole.
• Compiler is unique for each lang.
• Interpreter: It converts source code (program) into object code (binary form) as well as executes it line by line. It executes the statement before translating next statement.
• Assembler: Converts assembly language program into m/c language program.
APPLICATION SOFTWARE
Acquiring Software:
Commercial software
• Software that must be purchased
Stand alone products
• Solve one type of problem. E.g.: MSWord
Software suites
• Integrated tools that work together
• Solve many problems E.g.: MSOffice
Shareware
• Try before you buy
• May deactivate if not purchased
• Acquiring Software
Freeware
• No obligation to purchase
• Donations often accepted
• Software may be distributed freely
• Changes can be made.
Public domain software
• Similar to freeware
• Changes can be done.
Open source
• Programs distributed with source code
• Allows users to modify the software
• E.g.: Library management.
• Modifications and comments are welcome
• Often sold but sometimes available for free
• Linux and Open Office
•
Word Processing Programs
• Creates text documents
• Graphics and other objects are supported
• Professional quality can be achieved
• Simple web pages may be created
• Word Processing Programs
Interface
• Document area
• Menu bar
• Toolbars
• Rulers
• Scroll bars
• Status bars
•
Entering and editing text
• Text is entered by typing
• Cursor indicates position
• Blocks of text can be manipulated
• Most other programs include text tools
Formatting text
• Controls the document’s appearance
• Character formatting tools
Fonts
Type style
• Paragraph formatting tools
Line spacing
Tabs
• Document formatting tools
Margins
Headers
Spreadsheet Programs
• Calculates numbers and finances
• Data viewable in many ways
Tables
Graphs
• Complex calculations can be automated
Interface
• Rows, columns and cells
• Cell holds data or formulas
• Formula bar
• Labels describe cell contents
• Values
• Dates
• Formulas
Presentation Programs
• Creates slides or transparencies
• Complete set is a presentation
• Enhances a speech or lecture
• Color and animation enhance the slides
Interface
• Similar to a word processor
• Slide window
• Outline window
• Speaker notes
Creating a presentation
• Templates can simplify the process
• Build the slides
• Pick a layout
• Enter the desired text
• Apply special formatting
• Continue adding slides in order
• Apply slide transitions if desired
Presenting slide shows
• Use to enhance a speech
• Mouse click advances to next slide
• Physical transparencies on an overhead
• Computer screen delivery
• Large monitor delivery
• Data projector
Personal Information Managers
• PIM software
• Keep track of contact information
• Track upcoming events and times
• MS Outlook is popular
Data organization
• Contact information organized by last name
• Users may search for data
• Appointment reminders can be set
GRAPHICS
This Topic includes the following sections:
• Paint Programs
• Photo-Manipulation Programs
• Draw Programs
• Computer-Aided Design Programs
• 3-D Modeling Programs
• Animation
• Graphics and the World Wide Web
Paint Programs
• Paint programs work with bitmap images and manage the individual pixels that make up an image.
• Paint programs provide a variety of tools that can add special effects to an image.
• It can be difficult to edit an entity in a paint program because the program does not see the entity as a whole, but as a set of pixels. To edit the image, you must make changes to the pixels that comprise it.
Photo-Manipulation Programs
• Photo-manipulation programs are bitmap-based programs, which are used primarily to edit electronic or digitized photographs.
• Photo-manipulation programs can repair problems with an image, such as adjusting colors or hiding mistakes.
• Photo-manipulation programs can produce sophisticated effects, such as combining multiple images into a seamless whole, hiding parts of an image, and more.
Draw Programs
• Draw programs work with vectors and give the designer a great deal of flexibility in editing an image.
• Objects created in a draw program can be altered easily and without loss of image quality.
• Draw programs work well with text.
Computer-Aided Design Programs
• Computer-Aided Design (CAD) programs are used in technical design fields to create models of objects that will be built or manufactured.
• CAD software allows users to design objects in three dimensions (3-D) and to produce 3-D wireframe and solid models.
• CAD products provide the user with high precision, and enable the user to divide drawings into layers, and add accurate dimensions (measurements) to a drawing.
3-D Modeling Programs
Designers use 3-D modeling programs to build three-dimensional models of objects and characters, and to add special effects to them.
Modeling programs use four techniques to build models:
• Surface modeling
• Solid modeling
• Polygonal modeling
• Spline-based modeling
Animation
• Computers are used to create animation in various fields, including games and movies.
• Fly-bys and walk-through are basic types of computer animation.
• Character animation is the art of creating a character and making it move in a lifelike manner.
• Compositing tools allow designers to add characters and objects to scenes that did not originally contain them.
Graphics and the World Wide Web
• Web pages support many types of graphics, including bullets, rules, logos, complex artwork, and photographs.
• The GIF (Graphics Interchange Format) and JPEG (Joint Photographic Experts Group) image formats are the most widely used formats on the Web.
• Animation can be added to a Web page by using simple animated GIF images or plug-in software such as Flash or Shockwave.
MULTIMEDIA
This Topic includes the following sections:
• Multimedia, Interactivity, and New Media
• Information in Layers and Dimensions
• Hardware Considerations for Multimedia
• Applications for Multimedia
•
Multimedia, Interactivity, and New Media
• Multimedia
• Interactivity
• New Media and Digital Convergence
Multimedia, Interactivity, and New Media Defined - Multimedia
• A medium is a way of conveying information. Speech is one medium, text is another.
• There are many kinds of unique media. ("Media" is the plural of "medium.")
• Multimedia is the use of more than one type of medium at the same time to convey a message or information.
• A lecture presented along with slides is an example of a simple multimedia event.
Multimedia, Interactivity, and New Media Defined - Interactivity
• Like television, a PC can present many media types simultaneously. For example, text, animation, music, and narration can all play at one time.
• TV is not interactive; it only delivers content. The PC enables the use of interactive multimedia such as games and reference products.
• Interactivity means that the user and program respond to one another. The program provides an ever-changing array of choices, which the user selects to direct the flow of the program.
Multimedia, Interactivity, and New Media Defined - New Media and Digital Convergence
• "New media" is a term that encompasses all types of interactive multimedia technologies.
• New media bring together not only multimedia content, but delivery technologies such as cable, telephone lines, networks, and the Internet.
• New media is based on the concept of digital convergence, which means many different technologies can be used together to deliver different types of content in one digital stream.
Information in Layers and Dimensions
• The Importance of Content
• Hypermedia and Navigation
Information in Layers and Dimensions - The Importance of Content
• The purpose of multimedia is to make information (content) more interesting, compelling, or enjoyable, as well as easy to navigate.
• Multimedia technologies give users choices of the type of content that is presented, and the manner in which it is presented.
• Regardless of the technologies used in multimedia, the primary focus is on providing high-quality content.
Information in Layers and Dimensions - Hypermedia and Navigation
• The process of moving through electronic information is called navigation.
• Well designed multimedia products provide a variety of methods for the user to navigate and choose content. Multimedia navigation is based on “hypermedia”.
• Hypermedia allows different types of content to be linked together. By choosing a hyperlink, WWW users jump to a new web page or multimedia feature.
Hardware Considerations for Multimedia
• Most new PCs are multimedia-capable, featuring all the hardware required to play back multimedia content.
• To play multimedia content, a PC needs (at the very least) a sound card, speakers, and a CD-ROM or DVD-ROM drive. A large hard disk and lots of RAM are also helpful.
• New PCs must meet requirements set in the PC 97 or PC 99 standard to be considered multimedia-compliant.
Applications for Multimedia
• In the School
• In the Workplace
• In the Home
Applications for Multimedia - In the School
• Many types of multimedia tools are being used in schools, from CD-based reference products, to games, to online collaboration.
• Distance learning technologies allow schools to provide courses online, over the Internet. These online learning environments are called virtual universities.
Applications for Multimedia –In the Workplace
• Companies are increasingly using multimedia for sales, marketing, and training.
• Using computer-based training (CBT) products, companies can quickly and cost-effectively teach employees new skills.
• Because multimedia content can be distributed over the Web, many companies have developed online outlets which enable customers to view and purchase products from their PC.
Applications for Multimedia - In the Home
In the home, multimedia products are used largely for the following purposes:
• Reference materials
• Self-help and instruction
• Entertainment
This topic includes the following sections:
• How Computers Represent Data
• How Computers Process Data
• Factors Affecting Processing Speed
How Computers Represent Data:
• Binary Numbers
• The Binary Number System
• Bits and Bytes
• Text Codes
How Computers Represent Data– Binary Numbers
• Computer processing is performed by transistors, which are switches with only two possible states: on and off.
• All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.
• If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
How Computers Represent Data - Bits and Bytes
• A single unit of data is called a bit, having a value of 1 or 0.
• Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.
• Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.
• With one byte, the computer can represent one of 256 different symbols or characters.
How Computers Represent Data - Text Codes
• A text code is a system that uses binary numbers (1s and 0s) to represent characters understood by humans (letters and numerals).
• An early text code system, called EBCDIC (Extended Binary Coded Decimal Interchange Code), uses eight-bit codes, but is used primarily in older mainframe systems.
• In the most common text-code set, ASCII (American Standard Code for Information Interchange), each character consists of eight bits (one byte) of data. It specifies characters for values from 0 to 127. Extended ASCII specifies characters for values from 128 to 255. ASCII is used in nearly all personal computers.
• In the Unicode text-code set, each character consists of 32 bits (four bytes) of data. Mostly all characters used in word like Chinese, Korean and Japanese and mathematical symbols can be represented
How Computers Process Data
• Where Processing Occurs
• The Control Unit
• The Arithmetic Logic Unit
• Machine Cycles
• The Role of Memory in Processing
• Types of RAM
How Computers Process Data – Where Processing Occurs
• Processing takes place in the PC's central processing unit (CPU).
• The system's memory also plays a crucial role in processing data.
• Both the CPU and memory are attached to the system's motherboard, which connects all the computer's devices together, enabling them to communicate.
How Computers Process Data –The Control Unit
• The two main parts of a CPU are the control unit and the arithmetic logic unit (ALU)
• The control unit directs the flow of data through the CPU, and to and from other devices.
• The control unit stores the CPU's instruction set, which contains the list of instructions for all the tasks the CPU can perform.
• Each instruction is expressed in microcode a series of basic directions that tell the CPU how to execute more complex operations.
How Computers Process Data –The Arithmetic Logic Unit
• The actual manipulation of data takes place in the ALU.
• The ALU can perform arithmetic and logic operations.
• The ALU is connected to a set of registers—high speed memory locations built directly in to the CPU that are used to hold data and program instructions currently being processed.
How Computers Process Data –Machine Cycles
• To execute each instruction, the CPU follows a series of steps-called a machine cycle. The machine cycle includes two smaller cycles.
1. Instruction cycle
Fetching: Before the CPU can execute an instruction, the control unit must retrieve a command or data from memory
Decoding: Before execution, CU break down the command into instruction that corresponds to those in the instruction set.
2. Execution cycle
Executing: When the command is executed, the CPU carries out the instruction by converting them into micro codes.
Storing: CPU may be required to store the results of an instruction in memory
• CPU performance is measured in MIPS and BIPS.
• By using a technique called pipelining, many CPUs can process more than one instruction at a time.
• Multitasking by hyper threading (Pipelining).
The Role of Memory
• Nonvolatile memory: Permanent. ROM
• PROM chip ->Chip that cannot be changed .Used in printer and hard drives.
• ROM contains a set of start up instruction->BIOS.
• BIOS contain POST to ensure that the system is functioning properly and all expected hardware devices are present.
• Flash memory: Special type of nonvolatile memory used in portable digital devices like digital camera, portable MP3 player, USB.
• Volatile memory: Non permanent. RAM
Single in line memory module, Dual in line memory module
There are two basic types of RAM: static and dynamic
• Dynamic RAM (DRAM) chips must be recharged with electricity very frequently, or they will lose their contents. One transistor per bit, slower, cheaper, larger capacity
• Static RAM (SRAM) does not need to be recharged as often as DRAM, and can hold its contents longer.
To store and retrieve data CPU uses Memory address a number that indicates a location on the memory chip.
Factors Affecting Processing Speed
• Registers
• RAM
• The System Clock
• The Bus
• Cache Memory
Factors Affecting Processing Speed – Registers
• The CPU contains a number of small memory areas, called registers, which store data and instructions while the CPU processes them.
• The size of the registers (also called word size) determines the amount of data with which the computer can work at a one time.
• Today, most PCs have 32-bit registers; mean the CPU can process four bytes of data at one time. Register sizes are rapidly growing to 64 bits.
Factors Affecting Processing Speed – RAM
• The amount of RAM in a PC has a direct affect on the system's speed.
• The more RAM a PC has, the more program instructions and data can be held in memory, which is faster than storage on disk.
• If a PC does not have enough memory to run a program, it must move data between RAM and the hard disk frequently. This process, called swapping, can greatly slow a PC's performance.
• Process of swapping unused content of RAM to hard disk is called Virtual memory
Factors Affecting Processing Speed -The System Clock
• A single "tick" of the clock is the time required to turn a transistor off and back on. This is called a clock cycle.
• Clock cycles are measured in Hertz (Hz), a measure of cycles per second. If a computer has a clock speed of 300 MHz, then its system clock "ticks" 300 million times every second.
• The faster a PC's clock runs, the more instructions the PC can execute each second.
Factors Affecting Processing Speed -The Bus
• A bus is group of parallel wires. Each wire can transfer one bit at a time.
• Data bus is an electrical path between the components of a computer. Data and instructions travel along this bus.
• The data bus' width determines how many bits can be transmitted between the CPU and other devices.
• The address bus runs only between the CPU and RAM, and carries nothing but memory addresses for the CPU to use.
• Peripheral devices are connected to the CPU by an expansion bus.
Factors Affecting Processing Speed -Cache Memory
• Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.
• Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.
• CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache. Cache present resident as well as external to CPU is called Level-3(L3) cache.
• The amount of cache memory has a tremendous impact on the computer's speed.
Processors:
X= (A+B) * (C+D)
• RISC Processor- Reduced instruction set computing
Instruction set is small and the instruction is simple.
Y=A+B
Z=C+D
X=Y*Z
• CISC Processor–Complex instruction set computing
Instruction set is large and the instruction is complex.
X= (A+B) * (C+D)
MEMORY DEVICES
Types of ROM:
Mask ROM:
• It is permanently programmed during the manufacturing process according to the customer application.
• Once the memory is programmed it cannot be changed
PROM:
• In order to provide same flexibility in the application of ROM Programmable ROM (PROM) is introduced.
• It can be programmed electrically by the user but cannot be reprogrammed
• It is used in the control of electrical equipment such as washing machine and electric arm.
EPROM (Erasable Programmable ROM):
• A PROM device that can be erased and reprogrammed is called erasable PROM.
• To program a different data, all cells in the EPROM must be erased. This is done by illuminating the cells by a strong UV light having a wavelength typically 253.7 nm for about 20 minutes.
• It is provided with a transparent quartz window on the top of the chip to allow the UV rays for erasing the data.
• The window should be covered with an opaque sticker to protect the memory from unwanted exposure to UV rays from sunlight and fluorescent lamps.
• The new data can be stored by programming electrically thus EPROM is UV erasable and electrically programmable.
Disadvantages of EPROM:
• Changes in the selected memory locations cannot be made in the reprogramming
• The chip on the whole should be erased
• The EPROM IC must be removed from the circuit and then the memory is erased by exposing to UV light through a window. Thus it takes nearly 30 minutes.
EEPROM (Electrically Erasable PROM):
• It overcomes the disadvantages of ERPOM. It can be erased and programmed by the application of control electricity pulses to the IC in the circuit and thereby changes can be made in the desired portion of IC.
• EEPROM is nonvolatile like EPROM but does not require UV light for erasing.
• EEPROM is a low power semiconductor device and it occupies less space.
• It has the advantage of program flexibility, small size and semiconductor memory (low voltage and no mechanical parts).
Types of RAM:
Static RAM:
• It essentially contain an array of flip-flop one of each bit. Data written into flip-flop remains stored as long as the power is maintained.
• Memory capacity of static RAM varies from 64 bits to 1 Mega bits.
DRAM (Dynamic RAM):
• It is the lowest cost, highest density RAM available.
• Computers use DRAM for main memory storage with the memory size ranging from 16 Mega bytes to 256 Mega bytes.
• It stores its binary information in the form of electric charges on capacitors. Hence it must be recharged or refreshed 1000 of times every second in order to retain these stored charges.
• It uses integrated mass capacitor as basic memory cell instead of flip-flop.
Pseudo static RAM:
• It is basically a dynamic RAM. It has built in refresh logic. Hence no external refreshing circuit is required and there by Pseudo static RAM can be used as a static RAM device.
• When this device is performing internal refresh it cannot be accessed for read or write operation
• The capacity is 64 Kbits and more.
INPUT DEVICES
This Topic includes the following sections:
The Keyboard
The Mouse
Variants of the Mouse
The Keyboard
• The Standard Keyboard Layout
• Ergonomic Keyboards
• How a Keyboard Works
•
The Keyboard - Standard Keyboard Layout
• A standard computer keyboard has about 100 keys.
• Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters.
The Keyboard - Standard Keyboard Layout
Most keyboards have keys arranged in five groups:
• Alphanumeric keys
• Numeric keypad
• Function keys
• Modifier keys
• Cursor-movement keys
The Keyboard - Ergonomic Keyboards
• Ergonomics->Study of Physical relationship between people and their tools.
• Long periods of keyboard use can cause injuries.
• An ergonomically correct keyboard can help you to avoid repetitive stress (strain) injuries (RSI).
• You also can avoid injuries by adopting correct keyboarding practices.
The Keyboard - How a Keyboard Works
When you press a key:
• The keyboard controller detects the keystroke.
• The controller places a scan code in the keyboard buffer, indicating which key was pressed.
• The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke.
The Mouse - What is a Mouse?
• The mouse is a pointing device. You use it to move a graphical pointer on the screen.
• The mouse can be used to issue commands, draw, and perform other types of input tasks.
Variants of the Mouse
• Trackballs
• Track pads
• Integrated Pointed Devices
Types of Mouse
• 1.Mechanical Mouse
• 2.Optical Mouse (Non mechanical)
Mouse Function (Mechanical)
Mouse movesà Mouse ball spins the rollerà Roller gives information to the system softwareà System software controls the pointer
Mouse Function (Optical)
Mouse emits a beam of lightà From the Reflected light distance, direction and speed of pointer is evaluatedà System software controls the pointer.
The Mouse - Mouse Techniques:
Using the mouse involves five techniques:
Pointing; Move the mouse to move the on-screen pointer.
Clicking; Press and release the left mouse button once.
Double-clicking; Press and release the left mouse button twice.
Dragging; Hold down the left mouse button as you move the pointer.
Right-clicking; Press and release the right mouse button.
Variants of the Mouse - Trackballs
• A trackball is like a mouse turned upside-down & needs less working space.
• Use your thumb to move the exposed ball and your fingers to press the buttons.
Track pads:
• A track pad is a touch-sensitive pad that provides the same functionality as a mouse.
• To use a track pad, you glide your finger across its surface.
• Track pads provide a set of buttons that function like mouse buttons.
Integrated Pointing Devices
• An integrated pointing device is a small joystick built into the keyboard between G and H.
• To use an integrated pointing device, you move the joystick.
• These devices provide a set of buttons that function like mouse buttons
Alternative Input Devices – Devices for the Hand
• Pens
• Touch Screens
• Game Controllers
•
Devices for the Hand – Pens
• With a pen-based system, you use an electronic pen called as stylus to write on the screen and choose commands.
• Pens are common input devices for handheld computers, like personal digital assistants (PDAs) and tablet PC for collecting database
• Pens are handy for making notes or selecting commands, not for inputting a lot of text.
Devices for the Hand - Touch Screens
• Touch-screen systems accept input directly through the monitor.
• Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse.
• Touch-screen systems are useful for selecting options from menus.
• They are useful for ATM, information centre like railways, departmental stores etc.
Devices for the Hand - Game Controllers
• Game controller is an input device which accepts I/p from the user, process it, and produce o/p in the form of graphics and sound
• The two primary types of game controllers are joysticks and game pads.
• Game pads usually provide controls for each hand. They are flexible and used to control games
• Joysticks are popular for flight simulator and driving games. Some type includes steering wheel, gearshifts and foot pedals.
Alternative Input Devices –Optical Input Devices
• Bar Code Readers
• Image Scanners and OCR (Optical Character Recognition)
Optical Input Devices - Bar Code Readers
• Bar code readers can read bar codes—patterns of printed bars to identify the product.
• The reader emits light, which reflects off the bar code.
• A light sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.
• They tell the reader whether the barcode has been read right side up or upside down. Then it converts the individual bar patterns into corresponding code. Then the reader feeds the data into the computer.
• Flatbed bar code readers are commonly found in library, supermarkets. Courier services often use handheld readers.
Optical Input Devices: Image Scanners and OCR
• Image scanner converts any printed image into electronic form by shining light onto the image and sensing the intensity of light reflection at every point.
• Thus they digitize printed images for storage and manipulation in a computer.
• Color scanners use filters to separate the components of color into the primary additive color (RGB)
• After scanning, when it is a photo we can use photo shop application to change the properties of picture like adjusting contrast, changing color etc.
• Scanners come in a range of size from hand held model to flat bed scanners that sit on desktop.
• Hand held scanners or portable but require multiple passes to scan a single page because they are not wide as paper.
• Flat bed scanners offered high quality reproduction since it can scan a page in single pass (Xerox m/c).
• Some medium sized scanners are also available (FAX m/c).
OCR (Optical Character Recognisation):
• When it is a text document we can use Optical character recognition (OCR) software to translate scanned text into editable electronic documents.
• Image is first stored as bit map. A bit map is grid of dots; each dot is represented by one or more bits.
• OCR translates the array of dots into letters and numbers.
• For that, it looks at each character and tries to match the character with its own assumption. OCR extremely complex and not 100% accurate.
• It is used to convert the fax into editable document.
Alternative Input Devices – Audio-Visual (Multimedia) Input Devices
• Audio input Microphones and Speech Recognition
• Video Input PC video camera, Digital camera
Microphones and Speech Recognition
• Microphones can accept auditory input. A microphone requires a sound card in the PC.
• A sound card is a special device which translate analog sound signal from the microphone into digital codes the computer can store and process .This process is called digitizing. Vice-versa can also be done by sound card.
• By this we can record our voice and store it as file in computer. We can use it in presentations; webpage’s or email it to others.
• With speech recognition software (voice recognition), you can use your microphone to dictate text, navigate programs, and choose commands.
• SRS takes the smallest individual sound in a language called phonemes, and translate them into text.
• Some problem occurs are
1. Differentiating sound for e.g.: during the process of two and too.
2. To isolate background noise.
3. Need of pause between words.
• Newer software overcomes these problems by training with speech patterns and pronunciation.
• Other types of audio I/p are CD, tape player, radio…
MIDI-Musical Instrument Digital interface
A MIDI port or adapter is used to connect the musical instruments to computer.
Video Input
• Applications like video conferencing and video chat needs video files to be communicated between computers.
• PC video cameras digitize full-motion images and can transmit them in n/w. eg:webcam
• It breaks images into pixels and each pixel’s color and characteristics are stored as digital code.
• Video capture card is used to connect video devices to PC.
• Digital cameras are portable, handheld device that capture still images.
• Difference between normal film camera and digital camera.
• Video images may be compressed to use less memory and storage space for passing in network.
PRINTING DEVICES
Overview of Printers - Categorizing Printers
• Printers fall into two categories: Impact printers: use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper.Non-impact printers: use different methods to place ink (or another substance) on the page.
Dot Matrix Printers -How Do Dot Matrix Printers Work?
• Dot matrix printers are a common type of impact printer.
• A dot matrix printer's print head contains a cluster of pins. The printer can push the pins out to form patterns in rapid sequence.
• The pins press an inked ribbon against the paper, creating an image.
Dot Matrix Printers - Performance
• Lower-resolution dot matrix printers use nine pins. Higher-resolution models have 24 pins.
• Speed is measured in characters per second (cps). Some dot matrix printers print 500 cps.
Ink Jet Printers –How Do Ink Jet Printers Work?
• Ink jet printers are an example of non-impact printers.
• The printer sprays tiny droplets of ink onto the paper.
• Ink jet printers are available for color and black-and-white printing.
Ink Jet Printers - Performance
• Ink jet printers offer speeds of (2 – 4 pages per minute ppm) and resolution (300 – 600 dots per inch dpi), comparable to low-end laser printers. Ink jet printers are inexpensive and have low operating costs.
Laser Printers –How Do Laser Printers Work?
Laser printers are non-impact printers. They use heat and pressure to bond particles of toner to paper. Laser printers are available for color and black and white printing.
Laser Printers - Performance
• Laser printers provide resolutions from 300 – 1200 dpi and higher.
• Black-and-white laser printers usually produce 4 – 16 ppm.
• Laser printers produce higher-quality print than ink jet printers, but are more expensive.
Overview of Printers - Evaluating Printers
When evaluating printers, consider four criteria
• Image quality – Measured in dots per inch (dpi). Most printers produce 300 – 600 dpi.
• Speed – Measured in pages per minute (ppm) or characters per second (cps)
• Initial cost – Consumer printers cost $250 or less, but professional printers can cost thousands of dollars.
• Cost of operation – This refers to the cost of supplies used by the printer.
Photo printers
Used to print images that can be created by using Digital camera or scanner.
Thermal – Wax printer
• Presentation Graphics and handouts.
• Bold colors with heavy color requirement, posters or book covers.
• Ribbon coated with panels of colored Wax that melts and adheres to plain paper as colored dots when passed over a focused heat source.
Dye – Sublimation printers
• Get Realistic quality and color for photo images- Desktop publishers, artist.
• Ribbon containing panels of color is moved across a focused heat source.
• Capable of subtle temperature variations.
• The heated dyes evaporated from the ribbon and diffuse on specially coated paper.
• The variation to the color is related to the intensity of the color applied.
• Create sharp images. Slow.
Plotters
• Same like printer except that it is used to print large format images – construction drawings created by an architect.
• Early plotter: Mechanical device contains robotic arm used to draw images on paper.
• Table plotter: Two robotic arms contain colored ink pens.
• Two arms operating at right angles as they draw on a stationary paper.
• Large and complex table plotters are notoriously slow.
• Large complicated drawings can take several hours to print
Roller plotter – Drum plotter
• one drawing arm but moves the paper.
• The drawing arm moves side to side as the paper is rolled back and forth.
• Draw perfect circles and other geometric shapes.
• Mechanical plotters replaced by Thermal, electro static, ink jet plotters and dye – sub printers.
• These devices can also produces large size drawings are faster and cheaper than mechanical plotters
STORAGE DEVICES
This lesson includes the following sections:
• Categorizing Storage Devices
• Magnetic Storage Devices
• Optical Storage Devices
Categorizing Storage Devices
• Storage devices hold data, even when the computer is turned off.
• The physical material that actually holds data is called storage medium. The surface of a floppy disk is storage medium.
• The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.
• The two primary storage technologies are magnetic and optical.
The primary types of magnetic storage are:
• Diskettes (floppy disks)
• Hard disks
• High-capacity floppy disks
• Disk cartridges
• Magnetic tape
The primary types of optical storage are:
• Compact Disk Read-Only Memory (CD-ROM)
• Digital Video Disk Read-Only Memory (DVD-ROM)
• CD-Recordable (CD-R)
• CD-Rewritable (CD-RW)
• PhotoCD
Magnetic Storage Devices
• How Magnetic Storage Works
• Formatting
• Disk Areas
• Diskettes
• Hard Disks
• Disk Capacities
• Other Magnetic Storage Devices
Magnetic Storage Devices- How Magnetic Storage Works
• A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions.
• Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.
• A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.
Magnetic Storage Devices – Formatting
• Before a magnetic disk can be used, it must be formatted—a process that maps the disk's surface and determines how data will be stored.
• During formatting, the drive creates circular tracks around the disk's surface, and then divides each track into sectors.
• The OS (Operating System) organizes sectors into groups, called clusters, and then tracks each file's location according to the clusters it occupies.
Magnetic Storage Devices - Disk Areas
When a disk is formatted, the OS creates four areas on its surface:
• Boot sector – stores the master boot record, a small program that runs when you first start (boot) the computer
• File allocation table (FAT) – a log that records each file's location and each sector's status
• Root folder – enables the user to store data on the disk in a logical way
• Data area – the portion of the disk that actually holds data.
Magnetic Storage Devices – Diskettes
• Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies).
• Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium.
• Diskettes come in two sizes: 5.25-inch and 3.5-inch.
Magnetic Storage Devices - Hard Disks
• Hard disks use multiple platters, stacked on a spindle. Each platter has two read/write heads, one for each side.
• Hard disks use higher-quality media and a faster rotational speed than diskettes.
• Removable hard disks combine high capacity with the convenience of diskettes.
Magnetic Storage Devices - Disk Capacities
• Diskettes are available in different capacities, but the most common store 1.44 MB.
• Hard disks store large amounts of data. New PCs feature hard disks with capacities of 10 GB and higher.
Magnetic Storage Devices - Other Magnetic Storage Devices
• High-capacity floppy disks offer capacities up to 250 MB and the portability of standard floppy disks.
• Disk cartridges are like small removable hard disks, and can store up to 2 GB.
• Magnetic tape systems offer very slow data access, but provide large capacities and low cost.
Optical Storage Devices
• How Optical Storage Works
• CD-ROM
• CD-ROM Speeds and Uses
• DVD-ROM
• Other Optical Storage Devices
Optical Storage Devices – How Optical Storage Works
• An optical disk is high-capacity storage medium. An optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.
• When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).
Optical Storage Devices – CD-ROM
• In PCs, the most commonly used optical storage technology is called
Compact Disk Read-Only Memory (CD-ROM).
• A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio.
• Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.
Optical Storage Devices – CD-ROM Speeds and Uses
• Early CD-ROM drives were called single speed, and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 – 15 MBps).
• CD-ROM drives now can transfer data at speeds of up to 7800 KBps. Data transfer speeds are getting faster.
• CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions.
Optical Storage Devices - DVD-ROM
• A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.
• Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.
• DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.
Optical Storage Devices - Other Optical Storage Devices
• A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk.
• A CD-Rewritable (CD-RW) drive lets you record a CD, and then write new data over the already recorded data.
• PhotoCD technology is used to store digital photographs.
SYSTEM SOFTWARE
System ↔ System ↔ Application ↔ Computer
User Software Software System
System Software: It is a collection of programs designed to operate, control and extend processing capabilities of computer and which makes the operation of a computer system more effective and efficient.It comprises of1.Operating system2.Device driver3.System utility4.Language translators
Operating System:
A collection of programs used to control and coordinate the computer system. It manages functions performed by hardware, I/O devices, CPU, Secondary storage devices, communication and n/w equipment.
Functions of operating system:
• Memory management: It allocates and deallocates the memory of user program.
• Process management: Manages program in execution. It schedules CPU and shares the CPU among many processes.
• File management: Manages organization, naming, storing, retrieving, sharing and protection of files.
• Device management: Controls all the I/O devices and provides flexible and easy interface.
• Security management: Protects the system resources and information against destruction and unauthorized access.
• User Interface: It allows the user to give inst. And retrieve info. From the system.
Device Driver
• Special programs to extend the ability of OS in order to support I/O devices such as keyboard, mouse, monitor, printer…
• It contains all possible device dependent codes.
• It accepts request from device, translate it into commands for the appropriate device controller.
Computer System ↔ Device Driver ↔ I/O Device
System utility:
• Small program having specific tasks to perform which helps the user maintenance of system
Functions of system utility:
1. File management2. Backup3. Data recovery4. Virus protection5. Disk management6. Firewall7. Disk cleanup
Language Translator:
Tool that translates a programming language to m/c language which is understandable by a computer.
Categories of translators:
• Compiler: Converts high level language to m/c level language.or it converts source code (program) into object code (binary form) as a whole.
• Compiler is unique for each lang.
• Interpreter: It converts source code (program) into object code (binary form) as well as executes it line by line. It executes the statement before translating next statement.
• Assembler: Converts assembly language program into m/c language program.
APPLICATION SOFTWARE
Acquiring Software:
Commercial software
• Software that must be purchased
Stand alone products
• Solve one type of problem. E.g.: MSWord
Software suites
• Integrated tools that work together
• Solve many problems E.g.: MSOffice
Shareware
• Try before you buy
• May deactivate if not purchased
• Acquiring Software
Freeware
• No obligation to purchase
• Donations often accepted
• Software may be distributed freely
• Changes can be made.
Public domain software
• Similar to freeware
• Changes can be done.
Open source
• Programs distributed with source code
• Allows users to modify the software
• E.g.: Library management.
• Modifications and comments are welcome
• Often sold but sometimes available for free
• Linux and Open Office
•
Word Processing Programs
• Creates text documents
• Graphics and other objects are supported
• Professional quality can be achieved
• Simple web pages may be created
• Word Processing Programs
Interface
• Document area
• Menu bar
• Toolbars
• Rulers
• Scroll bars
• Status bars
•
Entering and editing text
• Text is entered by typing
• Cursor indicates position
• Blocks of text can be manipulated
• Most other programs include text tools
Formatting text
• Controls the document’s appearance
• Character formatting tools
Fonts
Type style
• Paragraph formatting tools
Line spacing
Tabs
• Document formatting tools
Margins
Headers
Spreadsheet Programs
• Calculates numbers and finances
• Data viewable in many ways
Tables
Graphs
• Complex calculations can be automated
Interface
• Rows, columns and cells
• Cell holds data or formulas
• Formula bar
• Labels describe cell contents
• Values
• Dates
• Formulas
Presentation Programs
• Creates slides or transparencies
• Complete set is a presentation
• Enhances a speech or lecture
• Color and animation enhance the slides
Interface
• Similar to a word processor
• Slide window
• Outline window
• Speaker notes
Creating a presentation
• Templates can simplify the process
• Build the slides
• Pick a layout
• Enter the desired text
• Apply special formatting
• Continue adding slides in order
• Apply slide transitions if desired
Presenting slide shows
• Use to enhance a speech
• Mouse click advances to next slide
• Physical transparencies on an overhead
• Computer screen delivery
• Large monitor delivery
• Data projector
Personal Information Managers
• PIM software
• Keep track of contact information
• Track upcoming events and times
• MS Outlook is popular
Data organization
• Contact information organized by last name
• Users may search for data
• Appointment reminders can be set
GRAPHICS
This Topic includes the following sections:
• Paint Programs
• Photo-Manipulation Programs
• Draw Programs
• Computer-Aided Design Programs
• 3-D Modeling Programs
• Animation
• Graphics and the World Wide Web
Paint Programs
• Paint programs work with bitmap images and manage the individual pixels that make up an image.
• Paint programs provide a variety of tools that can add special effects to an image.
• It can be difficult to edit an entity in a paint program because the program does not see the entity as a whole, but as a set of pixels. To edit the image, you must make changes to the pixels that comprise it.
Photo-Manipulation Programs
• Photo-manipulation programs are bitmap-based programs, which are used primarily to edit electronic or digitized photographs.
• Photo-manipulation programs can repair problems with an image, such as adjusting colors or hiding mistakes.
• Photo-manipulation programs can produce sophisticated effects, such as combining multiple images into a seamless whole, hiding parts of an image, and more.
Draw Programs
• Draw programs work with vectors and give the designer a great deal of flexibility in editing an image.
• Objects created in a draw program can be altered easily and without loss of image quality.
• Draw programs work well with text.
Computer-Aided Design Programs
• Computer-Aided Design (CAD) programs are used in technical design fields to create models of objects that will be built or manufactured.
• CAD software allows users to design objects in three dimensions (3-D) and to produce 3-D wireframe and solid models.
• CAD products provide the user with high precision, and enable the user to divide drawings into layers, and add accurate dimensions (measurements) to a drawing.
3-D Modeling Programs
Designers use 3-D modeling programs to build three-dimensional models of objects and characters, and to add special effects to them.
Modeling programs use four techniques to build models:
• Surface modeling
• Solid modeling
• Polygonal modeling
• Spline-based modeling
Animation
• Computers are used to create animation in various fields, including games and movies.
• Fly-bys and walk-through are basic types of computer animation.
• Character animation is the art of creating a character and making it move in a lifelike manner.
• Compositing tools allow designers to add characters and objects to scenes that did not originally contain them.
Graphics and the World Wide Web
• Web pages support many types of graphics, including bullets, rules, logos, complex artwork, and photographs.
• The GIF (Graphics Interchange Format) and JPEG (Joint Photographic Experts Group) image formats are the most widely used formats on the Web.
• Animation can be added to a Web page by using simple animated GIF images or plug-in software such as Flash or Shockwave.
MULTIMEDIA
This Topic includes the following sections:
• Multimedia, Interactivity, and New Media
• Information in Layers and Dimensions
• Hardware Considerations for Multimedia
• Applications for Multimedia
•
Multimedia, Interactivity, and New Media
• Multimedia
• Interactivity
• New Media and Digital Convergence
Multimedia, Interactivity, and New Media Defined - Multimedia
• A medium is a way of conveying information. Speech is one medium, text is another.
• There are many kinds of unique media. ("Media" is the plural of "medium.")
• Multimedia is the use of more than one type of medium at the same time to convey a message or information.
• A lecture presented along with slides is an example of a simple multimedia event.
Multimedia, Interactivity, and New Media Defined - Interactivity
• Like television, a PC can present many media types simultaneously. For example, text, animation, music, and narration can all play at one time.
• TV is not interactive; it only delivers content. The PC enables the use of interactive multimedia such as games and reference products.
• Interactivity means that the user and program respond to one another. The program provides an ever-changing array of choices, which the user selects to direct the flow of the program.
Multimedia, Interactivity, and New Media Defined - New Media and Digital Convergence
• "New media" is a term that encompasses all types of interactive multimedia technologies.
• New media bring together not only multimedia content, but delivery technologies such as cable, telephone lines, networks, and the Internet.
• New media is based on the concept of digital convergence, which means many different technologies can be used together to deliver different types of content in one digital stream.
Information in Layers and Dimensions
• The Importance of Content
• Hypermedia and Navigation
Information in Layers and Dimensions - The Importance of Content
• The purpose of multimedia is to make information (content) more interesting, compelling, or enjoyable, as well as easy to navigate.
• Multimedia technologies give users choices of the type of content that is presented, and the manner in which it is presented.
• Regardless of the technologies used in multimedia, the primary focus is on providing high-quality content.
Information in Layers and Dimensions - Hypermedia and Navigation
• The process of moving through electronic information is called navigation.
• Well designed multimedia products provide a variety of methods for the user to navigate and choose content. Multimedia navigation is based on “hypermedia”.
• Hypermedia allows different types of content to be linked together. By choosing a hyperlink, WWW users jump to a new web page or multimedia feature.
Hardware Considerations for Multimedia
• Most new PCs are multimedia-capable, featuring all the hardware required to play back multimedia content.
• To play multimedia content, a PC needs (at the very least) a sound card, speakers, and a CD-ROM or DVD-ROM drive. A large hard disk and lots of RAM are also helpful.
• New PCs must meet requirements set in the PC 97 or PC 99 standard to be considered multimedia-compliant.
Applications for Multimedia
• In the School
• In the Workplace
• In the Home
Applications for Multimedia - In the School
• Many types of multimedia tools are being used in schools, from CD-based reference products, to games, to online collaboration.
• Distance learning technologies allow schools to provide courses online, over the Internet. These online learning environments are called virtual universities.
Applications for Multimedia –In the Workplace
• Companies are increasingly using multimedia for sales, marketing, and training.
• Using computer-based training (CBT) products, companies can quickly and cost-effectively teach employees new skills.
• Because multimedia content can be distributed over the Web, many companies have developed online outlets which enable customers to view and purchase products from their PC.
Applications for Multimedia - In the Home
In the home, multimedia products are used largely for the following purposes:
• Reference materials
• Self-help and instruction
• Entertainment
Tuesday, November 20, 2007
Printing Devices
Overview of Printers - Categorizing Printers
- Printers fall into two categories:
Impact printers use a device to strike an inked ribbon, pressing ink from the ribbon onto the paper.
Non-impact printers use different methods to place ink (or another substance) on the page.
Dot Matrix Printers -
How Do Dot Matrix Printers Work?
How Do Dot Matrix Printers Work?
- Dot matrix printers are a common type of impact printer.
- A dot matrix printer's print head contains a cluster of pins. The printer can push the pins out to form patterns in rapid sequence.
- The pins press an inked ribbon against the paper, creating an image.
Dot Matrix Printers - Performance
- Lower-resolution dot matrix printers use nine pins. Higher-resolution models have 24 pins.
- Speed is measured in characters per second (cps). Some dot matrix printers print 500 cps.
Ink Jet Printers –
How Do Ink Jet Printers Work?
How Do Ink Jet Printers Work?
- Ink jet printers are an example of non-impact printers.
- The printer sprays tiny droplets of ink onto the paper.
Ink jet printers are available for color and black-and-white printing.
Ink Jet Printers - Performance
Ink jet printers offer speeds of (2 – 4 pages per minute ppm) and resolution (300 – 600 dots per inch dpi), comparable to low-end laser printers.Ink jet printers are inexpensive and have low operating costs.
Laser Printers –
How Do Laser Printers Work?
- Laser printers are non-impact printers.
They use heat and pressure to bond particles of toner to paper.
Laser printers are available for color and black-and-white printing.
- Laser printers provide resolutions from 300 – 1200 dpi and higher.
- Black-and-white laser printers usually produce 4 – 16 ppm.
Laser printers produce higher-quality print than ink jet printers, but are more expensive.
Laser Printers - Performance
Overview of Printers - Evaluating Printers
When evaluating printers, consider four criteria:
Image quality – Measured in dots per inch (dpi). Most printers produce 300 – 600 dpi.
Speed – Measured in pages per minute (ppm) or characters per second (cps)
Initial cost – Consumer printers cost $250 or less, but professional printers can cost thousands of dollars.
Cost of operation – This refers to the cost of supplies used by the printer.
Photo printers
1.Used to print images that can be created by using Digital camera or scanner.
Thermal – Wax printer
1.Presentation Graphics and handouts
2.Bold colors with heavy color requirement, posters or book covers
3.Ribbon coated with panels of colored Wax that melts and adheres to plain paper as colored dots when passed over a focused heat source.
Dye – Sublimation printers
1.Get Realistic quality and color for photo images- Desktop publishers, artist
2.Ribbon containing panels of color is moved across a focused heat source
3.Capable of subtle temperature variations.
4.The heated dyes evaporated from the ribbon and diffuse on specially coated paper .
5.The variation to the color are related to the intensity of the color applied.
6.Create sharp images. Slow.
Plotters
1.Same like printer except that it is used to print large format images – construction drawings created by an architect.
2.Early plotter : Mechanical device contains robotic arm used to draw images on paper
4.Two arms operating at right angles as they draw on a stationary paper
5.Large and complex table plotters are notoriously slow
6.Large complicated drawings can take several hours to print
Roller plotter – Drum plotter
1.one drawing arm but moves the paper
2.The drawing arm moves side to side as the paper is rolled back and forth
3.Draw perfect circles and other geometric shapes.
4.Mechanical plotters replaced by Thermal, electro static, ink jet plotters and dye – sub printers.
5.These devices can also produces large size drawings are faster and cheaper than mechanical plotters
Monday, November 19, 2007
System Software
System ↔ System ↔ Application ↔ Computer
User Software Software System
System s/w is a collection of programs designed to operate, control and extend processing capabilities of computer and which makes the operation of a computer system more effective and efficient.
It comprises of
1.Operating system
2.Device driver
3.System utility
4.Language translators
Operating System
Functions of operating system:
1.Memory management: It allocates and deallocates the memory of user prg.
2.Process management: Manages prg in execution. It schedules CPU and shares the CPU among many processes.
3.File management: Manages organization, naming, storing, retrieving, sharing and protection of
files.
4.Device management: Controls all the I/O devices and provides flexible and easy interface.
5.Security management: Protects the system resources and information against destruction and unauthorized access.
6.User Interface: It allows the user to give inst. And retrieve info. From the system.
Device Driver
- Special programs to extend the ability of OS in order to support I/O devices such as keyboard, mouse, monitor, printer…
- It contains all possible device dependent codes.
- It accepts request from device, translate it into commands for the appropriate device controller.
Computer System ↔ Device Driver ↔ I/O Device
System utility
- Small prg having specific tasks to perform which helps the user maintenance of system
- Functions of system utility:
1.File management
2.Backup
3.Data recovery
4.Virus protection
5.Disk management
6.Firewall
7.Disk cleanup - Functions of system utility:
- Language TranslatorTool that translates a programming language to m/c language which is understandable by a computer.
Categories of translators:
1.Compiler: Converts high level language to m/c level lang.
or it converts source code (prg) into object code (binary form) as a whole. Compiler is unique for each lang.
2.Interpreter: It converts source code (prg) into object code (binary form) as well as executes it line by line. It executes the statement before translating next statement.
3.Assembler: Converts assembly lang prg into m/c lang prg.Flowchart of Compiler
Flowchart of Interpreter
Process of Assembler
Types of OS
Monday, November 5, 2007
PROCESSING DEVICE - Notes
This topic includes the following sections:
• How Computers Represent Data
• How Computers Process Data
• Factors Affecting Processing Speed
How Computers Represent Data
•Binary Numbers
•The Binary Number System
•Bits and Bytes
•Text Codes
How Computers Represent Data
– Binary Numbers
•Computer processing is performed by transistors, which are switches with only two possible states: on and off.
•All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.
•If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
How Computers Represent Data - Bits and Bytes
•A single unit of data is called a bit, having a value of 1 or 0.
•Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.
•Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.
•With one byte, the computer can represent one of 256 different symbols or characters.
How Computers Represent Data - Text Codes
A text code is a system that uses binary numbers (1s and 0s) to
represent characters understood by humans (letters and
numerals).
•An early text code system, called EBCDIC, uses eight-bit codes, but is used primarily in older mainframe systems.
•In the most common text-code set, ASCII, each character consists of eight bits (one byte) of data. It specifies characters for values from 0 to 127. Extended ASCII specifies characters for values from 128 to 255. ASCII is used in nearly all personal computers.
•In the Unicode text-code set, each character consists of 32 bits (four bytes) of data. Mostly all characters used in world like chinese, korean and japanese and mathematical symbols can be represented
How Computers Process Data
Where Processing Occurs:
•The Control Unit
•The Arithmetic Logic Unit
•Machine Cycles
•The Role of Memory in Processing
•Types of RAM
How Computers Process Data –
Where Processing Occurs
•Processing takes place in the PC's central processing unit (CPU).
•The system's memory also plays a crucial role in processing data.
•Both the CPU and memory are attached to the system's motherboard, which connects all the computer's devices together, enabling them to communicate.
The Control Unit
The two main parts of a CPU are the control unit and the arithmetic logic unit (ALU)
•The control unit directs the flow of data through the CPU, and to and from other devices.
•The control unit stores the CPU's instruction set, which contains the list of instructions for all the tasks the CPU can perform.
•Each instruction is expressed in microcode a series of basic directions that tell the CPU how to execute more complex operations.
The Arithmetic Logic Unit
•The actual manipulation of data takes place in the ALU.
•The ALU can perform arithmetic and logic operations.
•The ALU is connected to a set of registers—high speed memory locations built directly in to the CPU that are used to hold data and program instructions currently being processed.
Machine Cycles
To execute each instruction, the CPU follows a series of
steps-called a machine cycle. The machine cycle includes
two smaller cycles.
1.Instruction cycle
Fetching :Before the CPU can execute an instruction, the
control unit must retrieve a command or data from
memory
Decoding: Before execution, CU break down the command into instruction that corresponds to those in the instruction set.
2. Execution cycle
Executing: When the command is executed, the CPU
carries out the instruction by converting them into
microcodes.
Storing: CPU may be required to store the results of an instruction in memory.
•CPU performance is measured in MIPS and BIPS.
•By using a technique called pipelining, many CPUs can process more than one instruction at a time.
•Multitasking by hyperthreading.
There are two basic types of RAM: static and dynamic
• Dynamic RAM (DRAM) chips must be recharged
with electricity very frequently, or they will lose their
contents. One transistor per bit, slower, cheaper,
larger capacity
• Static RAM (SRAM) does not need to be recharged
as often as DRAM, and can hold its contents longer.
To store and retrieve data CPU uses Memory address a number that indicates a location on the memory chip.
The Role of Memory
vNonvolatile memory: Permanent. ROM
§PROM chip ->Chip that cannot be changed .Used in printer and hard drives.
§ROM contains a set of start up instruction->BIOS.
§BIOS contains POST to ensure that the system is functioning properly and all expected hardware devices are present.
Flash memory: Special type of nonvolatile memory used in portable digital devices like digital camera, portable MP3 player, USB.
Volatile memory: Non permanent. RAM
Single in line memory module, Dual in line memory module
Factors Affecting Processing Speed
• Registers
• RAM
• The System Clock
• The Bus
• Cache Memory
Factors Affecting Processing Speed – Registers
•The CPU contains a number of small memory areas, called registers, which store data and instructions while the CPU processes them.
•The size of the registers (also called word size) determines the amount of data with which the computer can work at a one time.
•Today, most PCs have 32-bit registers, mean the CPU can process four bytes of data at one time. Register sizes are rapidly growing to 64 bits.
Factors Affecting Processing Speed – RAM
•The amount of RAM in a PC has a direct affect on the system's speed.
•The more RAM a PC has, the more program instructions and data can be held in memory, which is faster than storage on disk.
•If a PC does not have enough memory to run a program, it must move data between RAM and the hard disk frequently. This process, called swapping, can greatly slow a PC's performance.
•Process of swapping unused content of RAM to hard disk is called Virtual memory
The System Clock
•A single "tick" of the clock is the time required to turn a transistor off and back on. This is called a clock cycle.
•Clock cycles are measured in Hertz (Hz), a measure of cycles per second. If a computer has a clock speed of 300 MHz, then its system clock "ticks" 300 million times every second.
•The faster a PC's clock runs, the more instructions the PC can execute each second.
The Bus
•A bus is group of parallel wires. Each wire can transfer one bit at a time.
•Data bus is an electrical path between the components of a computer. Data and instructions travel along this bus.
•The data bus' width determines how many bits can be transmitted between the CPU and other devices.
•The address bus runs only between the CPU and RAM, and carries nothing but memory addresses for the CPU to use.
•Peripheral devices are connected to the CPU by an expansion bus.
Cache Memory
•Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.
•Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.
•CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache. Cache present resident as well as external to CPU is called Level-3(L3) cache.
•The amount of cache memory has a tremendous impact on the computer's speed.
X= (A+B) * (C+D)
RISC Processor- Reduced instruction set computing
Instruction set is small and the instruction is simple.
Y=A+B
Z=C+D
X=Y*Z
CISC Processor–Complex instruction set computing
Instruction set is large and the instruction is complex.
X= (A+B) * (C+D)
• How Computers Represent Data
• How Computers Process Data
• Factors Affecting Processing Speed
How Computers Represent Data
•Binary Numbers
•The Binary Number System
•Bits and Bytes
•Text Codes
How Computers Represent Data
– Binary Numbers
•Computer processing is performed by transistors, which are switches with only two possible states: on and off.
•All computer data is converted to a series of binary numbers– 1 and 0. For example, you see a sentence as a collection of letters, but the computer sees each letter as a collection of 1s and 0s.
•If a transistor is assigned a value of 1, it is on. If it has a value of 0, it is off. A computer's transistors can be switched on and off millions of times each second.
How Computers Represent Data - Bits and Bytes
•A single unit of data is called a bit, having a value of 1 or 0.
•Computers work with collections of bits, grouping them to represent larger pieces of data, such as letters of the alphabet.
•Eight bits make up one byte. A byte is the amount of memory needed to store one alphanumeric character.
•With one byte, the computer can represent one of 256 different symbols or characters.
How Computers Represent Data - Text Codes
A text code is a system that uses binary numbers (1s and 0s) to
represent characters understood by humans (letters and
numerals).
•An early text code system, called EBCDIC, uses eight-bit codes, but is used primarily in older mainframe systems.
•In the most common text-code set, ASCII, each character consists of eight bits (one byte) of data. It specifies characters for values from 0 to 127. Extended ASCII specifies characters for values from 128 to 255. ASCII is used in nearly all personal computers.
•In the Unicode text-code set, each character consists of 32 bits (four bytes) of data. Mostly all characters used in world like chinese, korean and japanese and mathematical symbols can be represented
How Computers Process Data
Where Processing Occurs:
•The Control Unit
•The Arithmetic Logic Unit
•Machine Cycles
•The Role of Memory in Processing
•Types of RAM
How Computers Process Data –
Where Processing Occurs
•Processing takes place in the PC's central processing unit (CPU).
•The system's memory also plays a crucial role in processing data.
•Both the CPU and memory are attached to the system's motherboard, which connects all the computer's devices together, enabling them to communicate.
The Control Unit
The two main parts of a CPU are the control unit and the arithmetic logic unit (ALU)
•The control unit directs the flow of data through the CPU, and to and from other devices.
•The control unit stores the CPU's instruction set, which contains the list of instructions for all the tasks the CPU can perform.
•Each instruction is expressed in microcode a series of basic directions that tell the CPU how to execute more complex operations.
The Arithmetic Logic Unit
•The actual manipulation of data takes place in the ALU.
•The ALU can perform arithmetic and logic operations.
•The ALU is connected to a set of registers—high speed memory locations built directly in to the CPU that are used to hold data and program instructions currently being processed.
Machine Cycles
To execute each instruction, the CPU follows a series of
steps-called a machine cycle. The machine cycle includes
two smaller cycles.
1.Instruction cycle
Fetching :Before the CPU can execute an instruction, the
control unit must retrieve a command or data from
memory
Decoding: Before execution, CU break down the command into instruction that corresponds to those in the instruction set.
2. Execution cycle
Executing: When the command is executed, the CPU
carries out the instruction by converting them into
microcodes.
Storing: CPU may be required to store the results of an instruction in memory.
•CPU performance is measured in MIPS and BIPS.
•By using a technique called pipelining, many CPUs can process more than one instruction at a time.
•Multitasking by hyperthreading.
There are two basic types of RAM: static and dynamic
• Dynamic RAM (DRAM) chips must be recharged
with electricity very frequently, or they will lose their
contents. One transistor per bit, slower, cheaper,
larger capacity
• Static RAM (SRAM) does not need to be recharged
as often as DRAM, and can hold its contents longer.
To store and retrieve data CPU uses Memory address a number that indicates a location on the memory chip.
The Role of Memory
vNonvolatile memory: Permanent. ROM
§PROM chip ->Chip that cannot be changed .Used in printer and hard drives.
§ROM contains a set of start up instruction->BIOS.
§BIOS contains POST to ensure that the system is functioning properly and all expected hardware devices are present.
Flash memory: Special type of nonvolatile memory used in portable digital devices like digital camera, portable MP3 player, USB.
Volatile memory: Non permanent. RAM
Single in line memory module, Dual in line memory module
Factors Affecting Processing Speed
• Registers
• RAM
• The System Clock
• The Bus
• Cache Memory
Factors Affecting Processing Speed – Registers
•The CPU contains a number of small memory areas, called registers, which store data and instructions while the CPU processes them.
•The size of the registers (also called word size) determines the amount of data with which the computer can work at a one time.
•Today, most PCs have 32-bit registers, mean the CPU can process four bytes of data at one time. Register sizes are rapidly growing to 64 bits.
Factors Affecting Processing Speed – RAM
•The amount of RAM in a PC has a direct affect on the system's speed.
•The more RAM a PC has, the more program instructions and data can be held in memory, which is faster than storage on disk.
•If a PC does not have enough memory to run a program, it must move data between RAM and the hard disk frequently. This process, called swapping, can greatly slow a PC's performance.
•Process of swapping unused content of RAM to hard disk is called Virtual memory
The System Clock
•A single "tick" of the clock is the time required to turn a transistor off and back on. This is called a clock cycle.
•Clock cycles are measured in Hertz (Hz), a measure of cycles per second. If a computer has a clock speed of 300 MHz, then its system clock "ticks" 300 million times every second.
•The faster a PC's clock runs, the more instructions the PC can execute each second.
The Bus
•A bus is group of parallel wires. Each wire can transfer one bit at a time.
•Data bus is an electrical path between the components of a computer. Data and instructions travel along this bus.
•The data bus' width determines how many bits can be transmitted between the CPU and other devices.
•The address bus runs only between the CPU and RAM, and carries nothing but memory addresses for the CPU to use.
•Peripheral devices are connected to the CPU by an expansion bus.
Cache Memory
•Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.
•Cache is located directly on the CPU or between the CPU and RAM, making it faster than normal RAM.
•CPU-resident cache is called Level-1 (L1) cache. External cache is called Level-2 (L2) cache. Cache present resident as well as external to CPU is called Level-3(L3) cache.
•The amount of cache memory has a tremendous impact on the computer's speed.
X= (A+B) * (C+D)
RISC Processor- Reduced instruction set computing
Instruction set is small and the instruction is simple.
Y=A+B
Z=C+D
X=Y*Z
CISC Processor–Complex instruction set computing
Instruction set is large and the instruction is complex.
X= (A+B) * (C+D)
STORAGE DEVICE - Notes
This lesson includes the following sections:
• Categorizing Storage Devices
• Magnetic Storage Devices
• Optical Storage Devices
Categorizing Storage Devices
•Storage devices hold data, even when the computer is turned off.
•The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium.
•The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.
•The two primary storage technologies are magnetic and optical.
• Categorizing Storage Devices
• Magnetic Storage Devices
• Optical Storage Devices
Categorizing Storage Devices
•Storage devices hold data, even when the computer is turned off.
•The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium.
•The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.
•The two primary storage technologies are magnetic and optical.
The primary types of magnetic storage are:
•Diskettes (floppy disks)
•Hard disks
•High-capacity floppy disks
•Disk cartridges
•Magnetic tape
The primary types of optical storage are:
•Compact Disk Read-Only Memory (CD-ROM)
•Digital Video Disk Read-Only Memory
(DVD-ROM)
•CD-Recordable (CD-R)
•CD-Rewritable (CD-RW)
•PhotoCD
Magnetic Storage Devices
• How Magnetic Storage Works
• Formatting
• Disk Areas
• Diskettes
• Hard Disks
• Disk Capacities
• Other Magnetic Storage Devices
Magnetic Storage Devices
- How Magnetic Storage Works
•A magnetic disk's medium contains iron particles, which can be polarized—given a magnetic charge—in one of two directions.
•Each particle's direction represents a 1 (on) or 0 (off), representing each bit of data that the CPU can recognize.
•A disk drive uses read/write heads containing electromagnets to create magnetic charges on the medium.
Magnetic Storage Devices - Formatting
•Before a magnetic disk can be used, it must be formatted—a process that maps the disk's surface and determines how data will be stored.
•During formatting, the drive creates circular tracks around the disk's surface, then divides each track into sectors.
•The OS (Operating System) organizes sectors into groups, called clusters, then tracks each file's location according to the clusters it occupies.
Magnetic Storage Devices - Disk Areas
When a disk is formatted, the OS creates four
areas on its surface:
•Boot sector – stores the master boot record, a small program that runs when you first start (boot) the computer
•File allocation table (FAT) – a log that records each file's location and each sector's status
•Root folder – enables the user to store data on the disk in a logical way
•Data area – the portion of the disk that actually holds data
Magnetic Storage Devices - Diskettes
•Diskette drives, also known as floppy disk drives, read and write to diskettes (called floppy disks or floppies).
•Diskettes are used to transfer files between computers, as a means for distributing software, and as a backup medium.
•Diskettes come in two sizes: 5.25-inch and 3.5-inch.
Magnetic Storage Devices - Hard Disks
•Hard disks use multiple platters, stacked on a spindle. Each platter has two read/write heads, one for each side.
•Hard disks use higher-quality media and a faster rotational speed than diskettes.
•Removable hard disks combine high capacity with the convenience of diskettes.
Magnetic Storage Devices - Disk Capacities
•Diskettes are available in different capacities, but the most common store 1.44 MB.
•Hard disks store large amounts of data. New PCs feature hard disks with capacities of 10 GB and higher.
Magnetic Storage Devices - Other Magnetic Storage Devices
•High-capacity floppy disks offer capacities up to 250 MB and the portability of standard floppy disks.
•Disk cartridges are like small removable hard disks, and can store up to 2 GB.
•Magnetic tape systems offer very slow data access, but provide large capacities and low cost.
Optical Storage Devices
• How Optical Storage Works
• CD-ROM
• CD-ROM Speeds and Uses
• DVD-ROM
• Other Optical Storage Devices
Optical Storage Devices –
How Optical Storage Works
•An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data.
•To store data, the disk's metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently.
•When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).
Optical Storage Devices –
CD-ROM
•In PCs, the most commonly used
optical storage technology is called
Compact Disk Read-Only Memory (CD-ROM).
•A standard CD-ROM disk can store up to 650 MB of data, or about 70 minutes of audio.
•Once data is written to a standard CD-ROM disk, the data cannot be altered or overwritten.
Optical Storage Devices –
CD-ROM Speeds and Uses
•Early CD-ROM drives were called single speed, and read data at a rate of 150 KBps. (Hard disks transfer data at rates of 5 – 15 MBps).
•CD-ROM drives now can transfer data at speeds of up to 7800 KBps. Data transfer speeds are getting faster.
•CD-ROM is typically used to store software programs. CDs can store audio and video data, as well as text and program instructions.
Optical Storage Devices - DVD-ROM
•A variation of CD-ROM is called Digital Video Disk Read-Only Memory (DVD-ROM), and is being used in place of CD-ROM in many newer PCs.
•Standard DVD disks store up to 9.4 GB of data—enough to store an entire movie. Dual-layer DVD disks can store up to 17 GB.
•DVD disks can store so much data because both sides of the disk are used, along with sophisticated data compression technologies.
Optical Storage Devices - Other Optical Storage Devices
•A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk.
•A CD-Rewritable (CD-RW) drive lets you record a CD, then write new data over the already recorded data.
•PhotoCD technology is used to store digital photographs.
INPUT DEVICES - Notes.
Standard Methods of Input
This Topic includes the following sections:
· The Keyboard
· The Mouse
· Variants of the Mouse
The Keyboard
•The Standard Keyboard Layout
• Ergonomic Keyboards
• How a Keyboard Works
The Keyboard - Standard Keyboard Layout
•A standard computer keyboard has about 100 keys.
•Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters.
The Keyboard - Standard Keyboard Layout
Most keyboards have keys arranged in five groups:
1. Alphanumeric keys
2. Numeric keypad
3. Function keys
4. Modifier keys
5. Cursor-movement keys
Ergonomic Keyboards
•Ergonomics->Study of Physical relationship between people and their tools.
•Long periods of keyboard use can cause injuries.
•An ergonomically correct keyboard can help you avoid repetitive stress (strain) injuries (RSI).
•You also can avoid injuries by adopting correct keyboarding practices.
The Keyboard - How a Keyboard Works
When you press a key:
•The keyboard controller detects the keystroke.
•The controller places a scan code in the keyboard buffer, indicating which key was pressed.
•The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke.
The Mouse - What is a Mouse?
•The mouse is a pointing device. You use it to move a graphical pointer on the screen.
•The mouse can be used to issue commands, draw, and perform other types of input tasks.
Variants of the Mouse
•Trackballs
•Trackpads
•Integrated Pointed Devices
Types of Mouse
1.Mechanical Mouse
2.Optical Mouse (Non mechanical)
Mouse Function (Mechanical)
Mouse movesà Mouse ball spins the rollerà Roller gives information to the system softwareà System software controls the pointer
Mouse Function (Optical)
Mouse emits a beam of light-> From the Reflected light distance, direction and speed of pointer is evaluated-> System software controls the pointer
The Mouse - Mouse Techniques
Using the mouse involves five techniques:
1.Pointing; Move the mouse to move the on-screen pointer.
2.Clicking; Press and release the left mouse button
once.
3.Double-clicking; Press and release the left mouse
button twice.
4.Dragging; Hold down the left mouse button as you
move the pointer.
5.Right-clicking; Press and release the right mouse button.
Variants of the Mouse - Trackballs
•A trackball is like a mouse turned upside-down & needs less working space.
•Use your thumb to move the exposed ball and your fingers to press the buttons.
Track pads
•A trackpad is a touch-sensitive pad that provides the same functionality as a mouse.
•To use a trackpad, you glide your finger across its surface.
•Trackpads provide a set of buttons that function like mouse buttons.
Integrated Pointing Devices
•An integrated pointing device is a small joystick built into the keyboard between G and H.
•To use an integrated pointing device, you move the joystick.
•These devices provide a set of buttons that function like mouse buttons
Alternative Input Devices –
Devices for the Hand
• Pens
• Touch Screens
• Game Controllers
Devices for the Hand - Pens
•With a pen-based system, you use an electronic pen called as stylus to write on the screen and choose commands.
•Pens are common input devices for handheld computers, like personal digital assistants (PDAs) and tablet PC for collecting database
•Pens are handy for making notes or selecting commands, not for inputting a lot of text.
Devices for the Hand - Touch Screens
•Touch-screen systems accept input directly through the monitor.
•Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse.
•Touch-screen systems are useful for selecting options from menus.
•They are useful for ATM, information centre like railways, departmental stores etc.
Devices for the Hand - Game Controllers
•Game controller is an input device which accepts i/p from the user, process it, and produce o/p in the form of graphics and sound
•The two primary types of game controllers are joysticks and game pads.
•Game pads usually provide controls for each hand. They are flexible and used to control games
•Joysticks are popular for flight simulator and driving games. Some type includes steering wheel, gearshifts and foot pedals
Alternative Input Devices –
Optical Input Devices
•Bar Code Readers
•Image Scanners and OCR (Optical Character Recognition)
Optical Input Devices - Bar Code Readers
•Bar code readers can read bar codes—patterns of printed bars to identify the product.
•The reader emits light, which reflects off the bar code.
A light sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.
•They tells the reader whether the barcode has been read right side up or upside down. Then it converts the individual bar patterns into corresponding code. Then the reader feeds the data into the computer.
•Flatbed bar code readers are commonly found in library, supermarkets. Courier services often use handheld readers.
Optical Input Devices :Image Scanners and OCR
•Image scanner convert any printed image into electronic form by shining light onto the image and sensing the intensity of light reflection at every point.
•Thus they digitize printed images for storage and
manipulation in a computer.
•Color scanners use filters to separate the components of color into the primary additive color (RGB)
•After scanning, when it is a photo we can use photo shop application to change the properties of picture like adjusting contrast, changing color etc.
•Scanners come in a range of size from hand held model to flat bed scanners that sit on desktop.`
•Hand held scanners or portable but require multiple passes to scan a single page because they are not wide as paper.
•Flat bed scanners offered high quality reproduction since it can scan a page in single pass (Xerox m/c).
•Some medium sized scanners are also available (FAX m/c).
OCR
•When it is a text document we can use Optical character recognition (OCR) software to translate scanned text into editable electronic documents.
•Image is first stored as bit map. A bit map is grid of dots, each dot is represented by one or more bits.
•OCR translate the array of dots into letters and numbers.
•For that, it looks at each character and tries to match the character with its own assumption. OCR extremely complex and not 100% accurate.
•It is used to convert the fax into editable document.
Alternative Input Devices –
Audio-Visual (Multimedia) Input Devices
• Audio input àMicrophones and Speech Recognition
• Video Input àPC video camera, Digital camera
Microphones and Speech Recognition
•Microphones can accept auditory input. A microphone requires a sound card in the PC.
•A sound card is a special device which translate analog sound signal from the microphone into digital codes the computer can store and process .This process is called digitizing. Vice-versa can also be done by sound card.
•By this we can record our voice and store it as file in computer. We can use it in presentations, webpages or email it to others.
•With speech recognition software (voice recognition), you can use your microphone to dictate text, navigate programs, and choose commands.
•SRS takes the smallest individual sound in a language called phonemes, and translate them into text.
•Some problem occurs are
1.Differentiating sound for eg: during the process of two and too.
2. To isolate background noise.
3. Need of pause between words.
• Newer software overcome these problems by training with speech patterns and pronunciation.
•Other types of audio i/p are CD, tape player, radio…
MIDI-Musical Instrument Digital interface
A MIDI port or adapter is used to connect the musical instruments to computer.
Video Input
•Applications like video conferencing and video chat needs video files to be communicated between computers.
•PC video cameras digitize full-motion images and can transmit them in n/w. eg:webcam
•It breaks images into pixels and each pixel’s color and characteristics are stored as digital code.
•Video capture card is used to connect video devices to PC.
•Digital cameras are portable, handheld device that capture still images.
•Difference between normal film camera and digital camera.
•Video images may be compressed to use less memory and storage space for passing in network.
This Topic includes the following sections:
· The Keyboard
· The Mouse
· Variants of the Mouse
The Keyboard
•The Standard Keyboard Layout
• Ergonomic Keyboards
• How a Keyboard Works
The Keyboard - Standard Keyboard Layout
•A standard computer keyboard has about 100 keys.
•Most keyboards use the QWERTY layout, named for the first six keys in the top row of letters.
The Keyboard - Standard Keyboard Layout
Most keyboards have keys arranged in five groups:
1. Alphanumeric keys
2. Numeric keypad
3. Function keys
4. Modifier keys
5. Cursor-movement keys
Ergonomic Keyboards
•Ergonomics->Study of Physical relationship between people and their tools.
•Long periods of keyboard use can cause injuries.
•An ergonomically correct keyboard can help you avoid repetitive stress (strain) injuries (RSI).
•You also can avoid injuries by adopting correct keyboarding practices.
The Keyboard - How a Keyboard Works
When you press a key:
•The keyboard controller detects the keystroke.
•The controller places a scan code in the keyboard buffer, indicating which key was pressed.
•The keyboard sends the computer an interrupt request, telling the CPU to accept the keystroke.
The Mouse - What is a Mouse?
•The mouse is a pointing device. You use it to move a graphical pointer on the screen.
•The mouse can be used to issue commands, draw, and perform other types of input tasks.
Variants of the Mouse
•Trackballs
•Trackpads
•Integrated Pointed Devices
Types of Mouse
1.Mechanical Mouse
2.Optical Mouse (Non mechanical)
Mouse Function (Mechanical)
Mouse movesà Mouse ball spins the rollerà Roller gives information to the system softwareà System software controls the pointer
Mouse Function (Optical)
Mouse emits a beam of light-> From the Reflected light distance, direction and speed of pointer is evaluated-> System software controls the pointer
The Mouse - Mouse Techniques
Using the mouse involves five techniques:
1.Pointing; Move the mouse to move the on-screen pointer.
2.Clicking; Press and release the left mouse button
once.
3.Double-clicking; Press and release the left mouse
button twice.
4.Dragging; Hold down the left mouse button as you
move the pointer.
5.Right-clicking; Press and release the right mouse button.
Variants of the Mouse - Trackballs
•A trackball is like a mouse turned upside-down & needs less working space.
•Use your thumb to move the exposed ball and your fingers to press the buttons.
Track pads
•A trackpad is a touch-sensitive pad that provides the same functionality as a mouse.
•To use a trackpad, you glide your finger across its surface.
•Trackpads provide a set of buttons that function like mouse buttons.
Integrated Pointing Devices
•An integrated pointing device is a small joystick built into the keyboard between G and H.
•To use an integrated pointing device, you move the joystick.
•These devices provide a set of buttons that function like mouse buttons
Alternative Input Devices –
Devices for the Hand
• Pens
• Touch Screens
• Game Controllers
Devices for the Hand - Pens
•With a pen-based system, you use an electronic pen called as stylus to write on the screen and choose commands.
•Pens are common input devices for handheld computers, like personal digital assistants (PDAs) and tablet PC for collecting database
•Pens are handy for making notes or selecting commands, not for inputting a lot of text.
Devices for the Hand - Touch Screens
•Touch-screen systems accept input directly through the monitor.
•Touch screens use sensors to detect the touch of a finger. They are useful where environmental conditions prohibit the use of a keyboard or mouse.
•Touch-screen systems are useful for selecting options from menus.
•They are useful for ATM, information centre like railways, departmental stores etc.
Devices for the Hand - Game Controllers
•Game controller is an input device which accepts i/p from the user, process it, and produce o/p in the form of graphics and sound
•The two primary types of game controllers are joysticks and game pads.
•Game pads usually provide controls for each hand. They are flexible and used to control games
•Joysticks are popular for flight simulator and driving games. Some type includes steering wheel, gearshifts and foot pedals
Alternative Input Devices –
Optical Input Devices
•Bar Code Readers
•Image Scanners and OCR (Optical Character Recognition)
Optical Input Devices - Bar Code Readers
•Bar code readers can read bar codes—patterns of printed bars to identify the product.
•The reader emits light, which reflects off the bar code.
A light sensitive detector identifies the bar code image by recognizing special bars at both ends of the image.
•They tells the reader whether the barcode has been read right side up or upside down. Then it converts the individual bar patterns into corresponding code. Then the reader feeds the data into the computer.
•Flatbed bar code readers are commonly found in library, supermarkets. Courier services often use handheld readers.
Optical Input Devices :Image Scanners and OCR
•Image scanner convert any printed image into electronic form by shining light onto the image and sensing the intensity of light reflection at every point.
•Thus they digitize printed images for storage and
manipulation in a computer.
•Color scanners use filters to separate the components of color into the primary additive color (RGB)
•After scanning, when it is a photo we can use photo shop application to change the properties of picture like adjusting contrast, changing color etc.
•Scanners come in a range of size from hand held model to flat bed scanners that sit on desktop.`
•Hand held scanners or portable but require multiple passes to scan a single page because they are not wide as paper.
•Flat bed scanners offered high quality reproduction since it can scan a page in single pass (Xerox m/c).
•Some medium sized scanners are also available (FAX m/c).
OCR
•When it is a text document we can use Optical character recognition (OCR) software to translate scanned text into editable electronic documents.
•Image is first stored as bit map. A bit map is grid of dots, each dot is represented by one or more bits.
•OCR translate the array of dots into letters and numbers.
•For that, it looks at each character and tries to match the character with its own assumption. OCR extremely complex and not 100% accurate.
•It is used to convert the fax into editable document.
Alternative Input Devices –
Audio-Visual (Multimedia) Input Devices
• Audio input àMicrophones and Speech Recognition
• Video Input àPC video camera, Digital camera
Microphones and Speech Recognition
•Microphones can accept auditory input. A microphone requires a sound card in the PC.
•A sound card is a special device which translate analog sound signal from the microphone into digital codes the computer can store and process .This process is called digitizing. Vice-versa can also be done by sound card.
•By this we can record our voice and store it as file in computer. We can use it in presentations, webpages or email it to others.
•With speech recognition software (voice recognition), you can use your microphone to dictate text, navigate programs, and choose commands.
•SRS takes the smallest individual sound in a language called phonemes, and translate them into text.
•Some problem occurs are
1.Differentiating sound for eg: during the process of two and too.
2. To isolate background noise.
3. Need of pause between words.
• Newer software overcome these problems by training with speech patterns and pronunciation.
•Other types of audio i/p are CD, tape player, radio…
MIDI-Musical Instrument Digital interface
A MIDI port or adapter is used to connect the musical instruments to computer.
Video Input
•Applications like video conferencing and video chat needs video files to be communicated between computers.
•PC video cameras digitize full-motion images and can transmit them in n/w. eg:webcam
•It breaks images into pixels and each pixel’s color and characteristics are stored as digital code.
•Video capture card is used to connect video devices to PC.
•Digital cameras are portable, handheld device that capture still images.
•Difference between normal film camera and digital camera.
•Video images may be compressed to use less memory and storage space for passing in network.
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