HUZAIFA JANI PROJECT : COMPUTER HARDWARE

TECHNICAL REPORT

Computer HardwareBy

MUHAMMAD HUZAIFA CH

National University of Modern Languages

H-9, Islamabad

COMPUTER HARDWARE

HARDWARE: The physical parts of a computer system are called hardware. Hardware can be

touched or seen by us.

INPUT DEVICES: A hardware component used to enter data and instructions into computer is

called input device. Some of the most commonly used input devices are Key board, mouse, scanner, light pen, digital camera (PC camera), joy stick, graphic table, touch screen etc.

1) KEY BOARD: A key board contains keys of (characters, letters, numbers, punctuation

marks, and special characters) pressing the relevant key tells the computer what to do or write. Alphabetic keys contains alphabets (A – Z and a- z) space bar, back space, special characters, numeric keys contains (0 – 9, +, -, /, *). Navigation keys are ←→↑↓. A key board also contains function keys from (F1 – F12) which perform different functions according to the application being run. It also contains modifier keys like (Ctrl, Alt, Del etc)

2) MOUSE: A mouse has a special ball beneath it that allows you to roll it around on a pad or

a desk, its movement guides the curser on the screen of the monitor. By clicking on the buttons of the mouse we give the computer directions what to do. There are other devices similar to the mouse that can be used in its place. Some of the alternate devices to the mouse are as under.

a) TRACK BALL: A track ball can be used as an alternate to the mouse. This device has

buttons similar to those on mouse. It has a large rotating ball on the top. The body of a track ball does not move. The ball is rolled with the finger tips and the position of the curser is controlled on the screen by rotating the ball.

b) TOUCH PAD: A touch pad is small and flat surface over which the user moves his finger

tip. The movement of the finger moves the curser on the screen. It is also known as track pad. A touch pad also has one or more buttons near it, these buttons work like mouse buttons. Touch pad is mostly used in note book computers.

c) POINTING STICK: It is a pressure sensitive device. It is similar to pencil eraser and

exists between the keys on the key board. The pointer on the screen moves when the user pushes the pointing stick.

3) GRAPHIC TABLE: It consists of a flat pad upon which a user draws images with a stylus pen.

It creates the same image on the screen.

4) TOUCH SCREEN: It is a video display screen that receives input from the touch of the

finger. The screen is covered with plastic layer. There are invisible beams of infrared light behind the screen. The user enters data by touching icons or menus on the screen. Touch screen is well suited for simple applications like ATM machines.

MUHAMMAD HUZAIFA CH National University of Modern Languages. H-9. Islamabad 2

5) DIGITAL SCANNER: It is an input device. It is used to read pictures and other printed materials placed on its glass surface. It reads the picture or printed material and translates it in digital form. Digital scanner uses laser technology to read the images.

6) DIGITAL CAMERA: It records photographs in the form of digital signals that can be stored directly in the computer memory. No chemical film is used in it.

7) LIGHT PEN: A light pen is a hand held pen like device. It is light sensitive stylus. It is

connected by a wire to the computer. It has a device at the tip that emittes light. The pen sends the information to the computer when user touches the pen on certain areas of a specially designed screen. Light pen is usually used by engineers, graphic designers and illustrators.

8) JOY STICK: A joy stick consists of a base and a stick. The stick can be moved in any

direction to move an object around the computer screen. A joy stick can perform a similar function to a mouse or track ball. The most common use of a joy stick is for playing computer games.

9) PEN BASED COMPUTER SYSTEM: Pen based system is used to enter hand writing and marks in computer by using pen like stylus instead of key board. The user writes word and symbols on the screen. The system uses hand writing recognition software that translates hand writing characters into useable and readable data. Pen based systems are commonly used to input signatures or messages that are stored and transmitted as a graphic image.

OUTPUT DEVICE: A hardware component used to display information to the user is called

output device. Some of the commonly used output devices are monitors, printers and speakers.

1) MONITOR: It looks a lot like a T.V. the monitor allows you to see what you and the

computer are doing together. Output displayed by the monitor is called soft copy. A monitor is also known as CRT (cathode ray tube) display screen or simply screen. Some of the chief features of a monitor are as follows. FEATURES OF DISPLAY SCREEN:

Different display screens can be distinguished on the basis of following features.

a) SIZE: Monitors are available in different sizes. The standard monitor for PC is in the size of 13” to 16”.

b) COLOUR: The display screen can be either monochrome or color. The color display screen can display output in multiple colors. The color display screen monitors are also called RGB (red, green. Blue) monitors. The RGB screen can create 256 colors and thousands of their variations.

The monochrome display screen displays output in single color. Monochrome display screen displays shows image s in a single color usually white, green, blue, red or amber color. However monochrome display screen can display different shades of the same color.

c) RESOLUTION: All characters and images on the screen are made of pixels and dots. Pixels are the dots or picture elements that form images on the monitor. Resolution of a monitor is the number of pixels on the screen. It is the image sharpness of a display screen. High number of pixels means high sharpness of image.

d) VIDEO DISPLAY ADAPTER: A display screen must have a video display

adapter attached with the computer, to display graphics. It is also called video graphic card (VGA). It is a circuit board that determines the following things;


i) Resolution. ii) Number of colors. iii) Speed with which images are displayed on the screen.

e) REFRESH RATE: The refresh rate is the speed with which a monitor re-draws the image on the screen. It is also known as vertical scan rate or vertical frequency. It is measured in Hertz. It indicates the number of times screen is refreshed in one second. The image on the screen appears more solid if the refresh rate is high. The refresh rate should be at least 72 Hertz. Common monitors have refresh rate between 75 to 85 hertz.

f) DOT PITCH: The distance between each pixel of a monitor is called dot pitch. It is also called pixel pitch. The distance between each pixel is measured in

Mili meters. Many monitors have a dot pitch of 0.26 or 0.28 mm. The smaller dot pitch means that there is less space between each pixel which results in brighter and Sharper image display.

TYPES OF DISPLAY SCREEN

a) CRT SCREEN: It is the most commonly used type of display screen. It looks like

T.V. it can display text as well as graphics. i) WORKING OF CRT MONITOR: It uses a cathode ray tube. CRT tube creates an image on screen by an electronic beam. CRT consists of one or more guns that fire a beam of electrons inside the screen. The screen is coated with very tiny phosphorus dots from inside. CRT in color monitors consists of three guns, these guns generate red, green and blue (RGB) colors. The other colors are generated with the combination of these three colors.

b) FLAT PANEL MONITORS: Laptop PC’s use flat panel monitors. These monitors take less space. Flat panel monitors use variety of technologies. The most common technology is called Liquid Crystal display (LCD). LCD monitors use much less power than the CRT monitors. These monitors are available in different sizes such as 15”, 17”, 18”, and 21”. LCD monitors creates images with a special tube of liquid crystals that is normally transparent but becomes solid when charged with electricity.

c) TOUCH SCREEN MONITORS: These are used for input as well as output. A touch screen is special type of visual display unit (VDU). It has a grid of light beams or fine wires on the screen. It allows the user to interact with the computer by the touch of a finger rather than typing on the key board or moving the mouse. The user enters data by touching icons or menus displayed on the screen. Touch screen is well suited for simple applications like ATM.

2) SPEAKERS & HEADPHONES: A type of output produced in the form of sound, voice or music is known as audio output. Speakers and headphones are two commonly used output devices for this type of output.

ORSpeakers and headphones are output devices that allow you to hear sound from your computer.Many PC’s have internal speakers but their quality of sound is very low. Some monitors also contain speakers on their sides. A device called woofer is used to boost the low base sound.

3) PRINTERS: A printer is an output device that prints characters, symbols, and graphics on paper. The printed output is called hard copy. Print resolution is measured in dots per inch. Different types of printers are as follows.


a) IMPACT PRINTERS: An impact printer, prints on the paper with the strike of hammer or pins on the ribbon. These printers work like a conventional type writer. Following are the main types of impact printers.

i) DOT MATRIX PRINTERS: Dot matrix printer is a character printer; it prints one character at a time. The printing pins of a dot matrix printer are arranged on a matrix. The number of pins in a matrix varies from 9*7 to 24*9. The pins in the printer are pressed forward by a magnetic device and the required character is printed. Dot matrix printer also prints in colors other than black by using color ribbon. Dot matrix printers are also used to print characters of other languages like Urdu, Arabic, Chinese and Hindi etc.

ii) DAISY WHEEL PRINTERS: It is a character printer. It is very much like a modern electronic type writer. The printing speed of this printer is in the range of 10 to 100 characters per second. Daisy wheel printer uses a printing wheel known as daisy wheel. Each petal of a daisy wheel has on it a fully formed character at its end. A motor rotates the wheel when the desired character reaches the printing position on the paper a hammer strikes the desired petal against the ribbon and the character is printed on the paper.

iii) LINE PRINTERS: Line printers are impact printers. These are of two types; (a) Drum printers: Drum printer is an impact ink printer it consists of a solid

cylindrical drum that has a complete character set around the drum in lines. Its speed ranges from 300 to 2500 lines per minute.

(b) Chain printers: it is another type of line printer. It uses a chain of printable characters wrapped around two pulleys. The chain rotates with very high speed to print the output or to fit the character of one line on the paper. Its speed ranges from 300 to 2500 lines per minute.

2) NON-IMPACT PRINTERS: Non impact printers use thermal, electrostatic, laser and inkjet technologies for printing. These printers are fast and produce high quality output as compared to impact printers. Some of the non impact printers are described below.

i) LASER PRINTERS: these are non impact printers. It is also called page printers because it prints one page at a time. A laser printer creates image on the paper by laser beam. Laser stands for light amplification by Stimulated Emission of Rays. Infact laser printers use the same technique to create image on the paper as photocopiers do. A full page of output is assembled in the printer buffer and its image is copied on the paper. Laser printers have very fast speed which ranges from 4 to 50 pages per minute. Color laser printers are also available to print text and graphics in different colors.

ii) INKJET PRINTERS: An inkjet printer is a non impact printer. It creates output on paper by a spray of ink from a fine spray jet. An electronic field controls the spraying jet that forms characters or graphs on the paper. When ink is sprayed on the paper it absorbs quickly. It is a character printer and prints one character at a time. Its quality is better than a dot matrix printer. The printing speed is up to 250 characters per second. Color inkjet printers are also available.

iii) THERMAL PRINTERS: Thermal printer uses heat technology to transfer ink to the paper. Thermal printer is the best color printer currently available but it is also very expensive. It was originally used in scientific labs to record data. Now this printer is widely used to produce very high quality color art work and text.

iv) PLOTTERS: A plotter is an output device that is used to produce quality image graphics in a variety of colors. Plotters are used to create maps, architectural drawings, graphs and charts. A plotter works by drawing line on paper using pens held in a mechanical arm. Different types of plotters are as following.

a) FLATBED PLOTTER: Flatbed plotters are used to plot or draw images. It contains pens for drawing images. The plotter is placed on a table like


surface. Software instructs the pens to move down on the paper. The pens then move s to create image on the paper. Most flatbed plotters have one or more pens of different colors and width.

b) DRUM PLOTTERS: Drum plotters use a rotating drum or cylinder. The drawing pens are mounted on the drum. The pens are moved to the right and left as the drum rotates. This movement creates the desired image. The

advantages of drum plotter are that the length of the plot is almost unlimited. The roll paper can be used to draw out very lengthy images. The width of

The image depends on the width of the drum.SYSTEM UNIT C.P.U:

CPU stands for central processing unit. It is the brain of the computer. It is also called processor. A computer cannot work without CPU. CPU is located on the mother board or the main board. It continuously receives instructions to execute. Each instruction tells CPU to process data. CPU performs all operations on data according to the given instructions. It executes instructions and tells other parts of the computer what to do. CPU consists of two main parts

1) ARITHEMATIC & LOGIC UNIT (ALU): ALU is a part of CPU. Actual execution of instructions takes place in this part. All the arithmetic and logical operations are performed in this part. It consists of two units.a) Arithmetic Unit: Arithmetic unit of ALU performs basic arithmetic functions like

addition, subtraction, multiplication and division (-, +,*, /).b) Logic Unit: Logical unit of ALU performs logical operations like comparing two data

items to find which data is greater than, equal to, lesser than, or not equal to (=,<,>,).

2) CONTROL UNIT: control unit is an important component of CPU. It acts like a traffic police man by controlling the movement of the data. Control unit controls the flow of data inside the computer system. It does not execute the instructions itself but infact directs other parts of the computer system to do so. Control unit directs and controls all the devices of the computer system. It tells the input device and secondary storage device what data and instructions are to read into the main memory, it also tells the ALU where the data is to be processed.

MEMORY: The component of a computer system that is used to store data and instructions is called memory. The data or instructions are stored either temporarily or permanent. There are two main types of computer memory.1) Primary Memory2) Secondary Memory

1) PRIMARY MEMORY: Primary memory is a temporary memory or storage. It is often refer to as main memory or internal memory. Following are some of the main types of primary memory.

a) Random Access Memory (RAM): RAM is a specified area inside the computer system in which data and information is stored and can easily be accessed, hence it is called primary memory. The data stored in this part of memory can be read, changed or erased completely and thus it’s called read and write memory. RAM is also called temporary memory or volatile memory. Because the information stored in it is lost when the computer is switched off. Some of the main types of RAM are as under.

i) D – RAM: DRAM stands for dynamic random access memory. It is like a Ram chip. A DRAM stores data in the form of an electronic charge or in the form of electronic switches having on/off states. Dynamic RAM stores information in IC’s (integrated circuits) containing capacitors, because capacitors loose their charge over time, this result in the loss of data contained in D RAM. In order to retain data in the D-RAM chip the chip is recharged or refreshed frequently. A small amount of electrical


energy is used to recharge it. During the recharging process the processor can not read or write the data in D-RAM. Recharging of chip decreases the processing speed of the chip.

ii) S – RAM: S-RAM stands for static random access memory. The S-RAM requires more power as compared to D-RAM but it does not need to be recharged frequently. Thus the term static is used. The computer processor does not have to wait to store data or to read it from the S-RAM chip during processing. It is faster and expensive than D-RAM.

2) SECONDARY MEMORY: It is much larger in size but much slower than main memory and is used for storing system, programes and other larger files. The main types of secondary memory are as follows.

a) Read Only Memory (ROM) : it is the type of memory that stores instructions permanently. Instruction or information stored in it can only be read but can not be deleted. It is not possible to edit the information contained in it. This is why it is called ROM. Unlike Ram the instructions stored in it are not loosed when the computer is switched off. Therefore it is called non-volatile memory. The information or instructions are stored in ROM at the time of manufacturing, and they become permanent inside the ROM. When the computer is switched on instructions inside the ROM are automatically loaded into the main memory. The main function of the information in ROM is to check different units of computer system during booting process and to load the operating system into the main memory. Some of the main types of ROM are as following.

i) P - ROM: PROM stands for programmable read only memory. In P-ROM the user can write its own instructions but that too only once. However once a programe is stored in P-ROM chip it cannot be changed or alter. If there is any error in writing the instructions into the P-ROM, the error cannot be removed and becomes unusable.

ii) E – PROM: It stands for erasable programmable read only memory. A user can erase instructions or data stored in E-PROM by exposing it to ultra-violet light and a new program can be written into the same chip. If there is any error in writing the instructions or data into the E-PROM, the user can erase it and can write a new program in its place. When an E-PROM is in use the data stored in it can only be read and remains permanent in the chip unless erased.

iii) E – EPROM: EEPROM stands for electrically erasable programmable read only memory. In this memory instructions can be erased and written with the help of electrical pulses. In EEPROM a user can write instructions or data inside the EEPROM chip with special electrical pulses. If there is any error in writing the instructions the user can erase contents electrically.

STORAGE DEVICES: Storage devices are used to store large volume of data and programes

permanently. Storage devices are also called backing storage devices, secondary storage devices or auxiliary storage devices. Secondary storage refers to storage device or media that is not in active use. The main reason for using these storage devices are as following. The main memory of a computer system is not permanent. That means the data stored in main memory in lost when computer is shut down. Also the main memory has a limited storage capacity. Two of the most important functions of a storage device are.

Reading: the process of copying data, instructions, or information from storage devices or media to memory is called reading.

Writing: The process of copying data, information or instructions from main memory to a storage device is called writing.


Following are some of the types of storage devices.

1) MAGNETIC TAPE: Magnetic tape is a flexible plastic tape coated with magnetic material. It is used widely when large amount of data is to be processed sequentially. An advantage of magnetic tape is that it is very cheap and economical storage medium. Its major disadvantage is that it is very slow in terms of processing speed.

2) MAGNETIC DISK: Magnetic disk is the most widely used for of storage medium. A magnetic disk is a thin, circular magnetic plate coated with magnetic material. Information can be read and write or stored on and from the magnetic surface. A disk must be formatted before it can be used. The formatting process prepares the disk for storing data. Formatting process creates track and sectors on the disk. Each track on the disk is divided into sectors. A sector is the smallest physical storage unit on a disk. Its size is normally 512 bytes. A magnetic disk is a random access memory or medium. It means that any part of the disk is directly accessible for the computer system.

Following are the types of magnetic disks which are described in brief.

a) FLOPPY DISK: Floppy disk is also simply called a diskette. It is a small flexible plastic disk coated with magnetic material. It was introduced by IBM in early 1970’s. It is a portable storage medium. Floppy disk can only store a small amount of data. The access speed of floppy disk is slower than the hard disk. It is inexpensive storage medium. The standard size of a floppy disk is 3.5” enclosed in a shell. A piece of metal covers the reading and writing area. It is called shutter. When the disk is inserted into a disk drive, the shutter opens to expose the surface of the disk. The jacket of the floppy disk has a notch at one side or corner. Moving the notch upwards closes the notch, and the disk is write protected.

b) HARD DISK: The hard disk is also called the fixed disk. It is the most popular medium of storage. It is the direct access storage device. It is made of one or more metal plates that are coated with magnetic material. The plates of the disk are permanently fixed in the hard disk drive. If there is more than one metal plate, each plate has its own read and write head. Data access is much faster than floppy disk. The speed of rotation of the plates is 7200 rounds per minute.

CHARACTERISTICS OF HARD DISK

i) Hard disk provides the large storage capacity. The capacity of computer hard disk is from 2 to 200 GB and more.

ii) It is much faster than floppy disk.iii) It is the primary medium for storing data and programes.iv) It is more reliable than floppy disk.v) Data stored on hard disk is safer than floppy disk.

3) ZIP DISK: Zip disk is a portable disk it has more storage capacity than floppy disk. Its storage capacity is up to 1000 MB. Zip disk can be read or written using zip drive. It is used for taking the backup of large data.

4) SUPER DISK: Super disk is produced by Imation. Its capacity is 120 MB. Super disk drive can also read the standard 1.44 MB floppy disk.

OPTICAL DISK: Optical disk uses LASER technology to read and write data. Optical disks are

also called compact disks (CD). They are available in 5.25” and 3.5” sizes. The laser stands for Light Amplification by Stimulated Emission of Rays. Laser beam writes on the surface of optical device by creating pits in the disk. Optical drive read data by focusing laser beam on the surface of the disk. A laser detects the presence of a pit. Optical disk’s storage capacity ranges from 100 Mb to 1 GB. Compact disk is removable and can be used from one computer to another like a floppy disk. Different categories of optical disks are as follows.


1) COMPACT DISK (CD): It is the most widely used medium of storage today. A single CD can store from 600 Mb to 1 GB of data. The contents of CD can be read by using CD drive. The rotational speed of CD drive indicates the speed of transferring data from CD. E.g. a 24x CD can transfer 3.6 MB of data per second. A 32x CD can transfer 4.8 MB of data per second.

TYPES OF CD’s

a) CD ROM: CD Rom stands for compact disk read only memory. The data stored on CD ROM can only be read and can not be deleted or changed. CD ROM is a portable storage device. The data can be transferred easily by using CD ROM drive. It can store about 700 MB’s of data.

b) CD – R: CD-R stands for compact disk recordable. The user can write data on CD-R for once only. But can read it many times. The data written on CD-R can not be erased. CD-R drives are known as CD Burners. The process of putting information into the CD is called burning the CD.

c) CD – RW: It stands for compact disk re-writeable. It is also known as erasable optical disk. The user can write data on CD-RW many times by erasing the existing data or contents. The most commonly used erasable and re-writeable disk is magnetic optical disk. It uses the technology of both magnetic and optical disks. Such disks are normally used for applications using large volume of storage with little up date activity.

2) DVD: DVD stands for digital video disk. It is similar to CD-ROM. It uses a laser beam with short wave length. Laser reads holes or pits on the disk. Data storage capacity of the disk is increased if the hole or pit size is small, so the storage capacity of DVD-ROM is much greater than CD-ROM because it uses a short wave length beam which creates small pits on it. It can store up to 17 GB’s of data.

TYPES OF DVD

a) DVD – R: DVD-R stands for digital video disk recordable. It is similar to CD-R disk. The user can write data on it for once only. But it can be read many times. Data written on it is permanent and cannot be erased.

b) DVD – RW: DVD-RW stands for digital video disk re-writeable. The user can write data on DVD-RW many times by erasing the existing data or contents.

SOLID STATE STORAGE DEVICES: The solid state storage devices or flash memory devices are unique among all the

storage devices. These devices do not use disk or tape for data storage and they have no moving part. These devices are neither magnetic nor optical. Solid state storage devices rely on integrated circuits to save or store data. Some solid state storage devices are portable and provide fast access to the data. They use very little power. These devices are very useful to store data on mobile devices and to transfer data from one device to another. It is widely used in digital camera, mp3 players, note book computers, PDA’s and cell phones.

TYPES OF SOLID STATE STORAGE DEVICES

1) USB FLASH DRIVE: USB flash drives are also known as pen drives or keychain drives. It provides much greater storage capacity than floppy disk and zip disk. A flash drive can store up to 8 GB’s of data. It can be plugged into any USB port. It is small and light weight storage device. USB flash drive requires no card reader.


2) FLASH MEMORY CARDS: these cards are widely used in PDA’s, digital cameras, and notebook computers. Generally these cards are not inter-changeable. Different types of flash memory cards are as follows.

a) COMPACT FLASH (CF): Compact flash card is about the size of a match box. It provides high storage capacity and access speed. It includes a built in controller to read and write data. It is very useful to be used in digital camera that requires MB’s of storage for each photo. It comes in various capacities of 512 MB up to 1 GB.

b) MULTI-MEDIA CARDS (MMC): It provides solid state storage in a package of precisely of the size of a postage stamp. It was initially used in mobile pones and pagers. It is now used with digital cameras and MP3 players. It includes a built in controller. MMC readers are economical and inexpensive.

c) SECURE DIGITAL CARDS (SDC): SDC is based on multi media card technology. It provides faster data transfer rate. It also includes cryptographic security protection stored data and music. It is popular for MP3 players.

d) SMART MEDIA CARD (SMC): SMC is originally called solid state floppy disk card as it looks like a floppy disk. It does not include a built in controller. It means smart media reader manages read and write process. It is the least durable media and should be handled with care.

e) XD PICTURE CARD: It is a flash memory card that looks like a rectangular piece of plastic. It is slightly larger than a penny with one of its edge curved. The capacity of XD card is from 16 MB to an expected 8 GB’s.

f) MEMORY STICK MEDIA: It is a flash memory card about the width of a penny. It was developed by SONY Incorporation Japan. MSM comes in different capacities between 4 MB to 1 GB.

FACTORS AFFECTING PROCESSING SPEED: Following are some important factors that affect the processing speed of a computer. They are briefly described below

1) REGISTERS: Register is a small high speed memory inside a CPU. CPU contains a number of registers to store data and instructions while the CPU processes them. The size of the register is also called a word size. It determines the amount of data with which a computer can work at one time. The size of register is in bytes. A register can be of 1, 2, 4, 8, 16, and 32 bytes. A computer with 32 bytes register enables CPU to process 4 bytes of data at one time. Bigger the size of register the bigger will be the performance of the computer.

2) RAM: Amount of RAM directly affects the processing speed of the computer. Higher amount of RAM mean that more size of data, instructions and programs can be stored or loaded in the main memory of the computer. If computer does not have enough memory to run a program, it will compel it to move data between RAM and hard disk frequently. This process is called swapping that can greatly slow down the performance of the computer system.

3) SYSTEM CLOCK: System clock is an electronic component. It generates electric signals at a fast rate. The time required to execute a single instruction is called clock speed. Clock speed tells us how much time a CPU takes to execute each instruction. CPU takes from 1 to 6 clock ticks to execute one instruction. Clock speed is measured as cycles per second. Its unit is hertz. If a computer has a clock speed of 300 MHz, its system clock ticks 300 million times every time. A faster clock can execute more instruction each second.

4) THE BUS: A bus is a path between the components of the computer. Data and instructions travel along these paths. The bus width determines that how many bits can be transmitted between the CPU and other devices. Bus width also affects the performance of


the computer. A higher bus width means that the computer can carry larger amount of data.

5) CASHE MEMORY: A cache pronounces cash, is high speed memory that holds the most recent data and instructions that have been loaded by the CPU. It is designed to speed up the transfer of data and instructions. Cache is located directly on the CPU or at the near most place. It is faster than RAM, the data and instruction is stored in cache. Next time when the CPU requires that data it first looks in cache memory. If the required data is found there it is retrieved from here instead of main memory. It speeds up the working of a CPU.

COMPUTER BUSES: Buses are the electrical paths or lines inside the computer along which

the data travels between different components of computer system in the form of electrical signals. One line of wire can carry one bit at a time. The capacity of computer bus depends upon the number of data lines it contains. An 8 bit bus can carry 8 bits of data from one component to another at a time. CPU communicates with other components of computer through buses. Different types of buses are as follows.

1) SYSTEM BUSES: System bus is a type of computer bus that is used to connect the main components of a computer such as CPU and main memory. System buses are part of mother board. Computers normally have system buses of 70 to 100 lines. Different type of system buses are as under.

a) DATA BUS: Electrical through which data is transferred between components of computer. The data bus consists of 8, 16, 32, and 64 separate lines. A 64 line data bus can transfer 64 bits of data at a time. It indicates the width of data bus; it has a direct impact on the system performance. The data bus lines are bi-directional. It means that CPU can read data from memory using these lines and write data to the memory location by using these lines.

b) ADDRESS BUS: Many components are connect to each other through buses. Each component is assigned a unique ID. This ID is called the address of that component. If a component wants to communicate with another component it uses address bus to specify the address of that component. The address bus is uni-directional. It can carry information only in one direction. It carries address of memory location from micro processor to main memory.

c) CONTROL BUS: Control bus is used to transmit different commands or control signals from one component to another component. A control signal contains the following;

i) Timing Information: It specifies the time which a device can use and address bus.ii) Command Signal: It specifies the type of operation to be performed. E.g. if the

CPU wants to read data from main memory, it uses control bus to send the memory read command to the main memory of the computer.

2) EXPANSION BUS: Expansion bus is a type of computer bus that is used to connect CPU with peripheral devices, such as mouse, key board, printer, modem and scanner etc.

DATA TRANSFER FROM CPU TO MEMORY: Data is transferred from CPU to the main

memory by using address bus and data bus. The process of transferring data from CPU to memory consists of the following different steps.

i) CPU places the address of main memory on the address bus.ii) CPU places the address of the data location on the data bus.iii) Main memory sees the address on address bus.iv) Main memory writes the data on specified location in the main memory


TERMINALS: Terminal is a device that performs input and output. It consists of a monitor,

keyboard, and a VGA card. Different types of terminals are as follows.

1) DUMB TERMINAL: It has no processing power and can not perform any function as independent device. It can enter and transmit data to a computer to which it is connected. Dumb terminal is normally connected to a host computer. Host computer performs the processing and then sends the output back to the dumb terminal.

2) INTELLIGENT TERMINAL: It also contains memory and processor to perform some functions independent of the host computer. It is also called programmable terminal.

3) SPECIAL PURPOSE TERMINAL: It performs specific tasks and is for use in particular industry.

PORTS: A port is an interface or a point of attachment. It is used to connect peripheral devices

with the computer system, such as mouse, keyboard, printers etc. each type of port operates at a certain speed. The speed is measured in kilobits per second (kbps) or megabits per second (mbps). Different types of port are as following.

1) SERIAL PORTS: A type of port that transmit one bit at a time is called serial port. It is usually used to connect devices that do not require fast data transmission like mouse and keyboard etc. serial port is often referred to as communication port (com port). Data travels over a serial port at 115 kbps.

2) PARALLEL PORT: Parallel port is used to connect devices that transfer many bites at a time. It is usually used to connect devices that require fast data transmission like printers and scanners etc. parallel ports are often referred to as line printers. The speed of parallel ports is 12 mbps. It is faster than serial ports.

REFERENCES :

WIKIPEDIA-COMPUTER HARDWARE BLOG-COMPUTER HARDWARE INTRODUCTION TO COMPUTING ( BOOK) DESCOVERING COMPUTERS BY “ SHELLY CASHMAN “ (BOOK) W3SCHOOLS.COM (WEBSITE ) ALISON.COM (WEBSITE) COMPUTER HARDWARE (BOOK) COMPUTER HARDWARE BASICS


HUZAIFA JANI PROJECT : COMPUTER HARDWARE

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