Components of Computer
Computer
components can be broadly divided into two categories :-
1. Hardware
1. Hardware
It refers to physical
component of a computer we can touch or see. For example, CPU, Monitor,
Keyboard, Hard Disk, Floppy Disk, etc.
Types of Hardware
Types of Hardware
The
hardware components of a microcomputer can be classified into the following
types:
(a)
Motherboard
(b)
Central Processing Unit or Processor
(c)
Input Devices
(d)
Output Devices
(e)
Computer Memory and Mass Storage Devices
(f) Solid state backing storage
(f) Solid state backing storage
(a) Motherboard
It also known as system
board is the most important hardware component of a microcomputer. A
motherboard contains the CPU chip, memory chip (ROM and RAM), I/O interface
controller, expansion slots and many other logic circuits. Motherboard include sound
cards, video cards, network cards, hard drives, or other forms
of persistent storage; TV tuner cards, cards providing
extra USB or FireWire slots and a variety of other custom components.
(b) CPU
Alternatively referred to as
the brain of the computer, processor, central processor, or microprocessor,
the CPU (pronounced as C-P-U), short for Central Processing Unit,
was first developed
at Intel with the help of Ted Hoff in the early 1970's. The
computer CPU is responsible for handling
all instructions it receives from
hardware and software running on the computer.
Components
of the CPU
1. Arithmetic
Logic Unit (ALU) - All calculations and comparisons, based on the instructions provided, are carried out within the ALU. It performs arithmetic functions like addition, subtraction, multiplication, division and also logical operations like greater than, less than and equal to etc.
2. Control
Unit(CU) - Controlling of all operations like input, processing and output are performed by control unit. It carries out instructions and tells the
rest of the computer
system what to do. It controls and coordinates computer components. It extracts
instructions from memory
and decodes and executes them.
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3. Registers/Memory
Unit - Registers are temporary storage areas which are responsible for holding
the data that is
to be processed. They store the instructions and data in a processor. This data
is further used by
Control Unit.
Functional
Units of a CPU or How a computer works?
a.
Input Unit - This unit is used for entering data and programs into the computer
system by the user for processing.
b.
Storage Unit - The storage unit is used for storing data and instructions before
and after processing.
c.
Output Unit - The output unit is used for storing the result as output produced
by the computer after processing.
d.
Processing - The task of performing operations like arithmetic and logical
operations is called processing. The Central Processing Unit (CPU) takes data
and instructions from the storage unit and makes all sorts of calculations
based on the instructions given and the type of data provided. It is then sent
back to the storage unit.
(c) INPUT DEVICES
Input
devices accept data and instructions from the user.
Following
are the examples of various input devices, which are connected to the computer
for this purpose.
1.
Keyboard
2. Mouse
3.
Light Pen
4.
Optical/magnetic Scanner
5.
Touch Screen
6.
Microphone for voice as input
7.
Track Ball
8.
Joystick
9. Bar codes
10.
Digital camera
11.
Magnetic ink character recognition (MICR)
12.
Joystick
13. Optical
Mark Readers
1. Keyboard
A keyboard
is the most common input device. The keyboard in most common use is the QWERTY
board. Generally
standard keyboard has 104 keys. Computer keyboards are QWERTY KEYBOARDS. The alphabetic
keys are arranged so that the upper-left row of letters begins with the six
letters Q W E R T Y.
2. Mouse
A device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard and flat surface. Its name is derived from its shape, which looks a bit like a mouse. As you move the mouse, the pointer on the display screen moves in the same direction.
3. Light pen
An input device that
utilizes a light-sensitive detector to select objects on a display screen. A
light pen is similar to a mouse, except that with a light pen you can move the
pointer and select objects on the display screen by directly pointing to the
objects with the pen.
4. Optical Scanner
Scanner is an input
device that can read text or illustration printed on paper and translates the
information into a form that the computer can use. A scanner works by
digitizing an image. It can scan typed documents,
pictures, graphics or even handwriting into a computer. Photographs
scanned into a microcomputer appear clearly on the screen and can be displayed whenever
desired.
5. Touch Screen
It works whenever you
touch any Touch Screen Device for example Latest Mobile, ATM, Kiosk Machine
& etc. Touch panel displays and pads are now being offered as alternatives
to keyboard. Here the input can be given through the computer screen that
accepts the input through monitor; users touch electronic buttons displayed on
the screen or they may use light pen.
6. Microphone
Microphone is an input
device, which takes voice as input. The voice communication is more error-prone
than information through keyboard. There are two types of microphones available
1.
Desktop Microphone
2.
Hand held Microphone
7. Track Ball
A trackball is an input
device used to enter motion data into computers or other electronic devices. It
serves the same purpose as a mouse, but is designed with a moveable ball on the
top, which can be rolled in any direction.
8. Joystick
The joystick is a vertical
stick which moves the graphic cursor in a direction the stick is moved. It
typically has a button on top that is used to select the option pointed by the cursor.
Joystick is used as an input device primarily used with video games, training
simulators and controlling robots.
9. Bar codes
A bar code is a set of
lines of different thicknesses that represent a number. Bar-code readers are
photoelectric scanners that read the bar codes or vertical zebra strips marks,
printed on product containers. These devices are generally used in super
markets, bookshops etc
10. Digital camera
A digital camera can
store many more pictures than an ordinary camera. Pictures taken using a digital camera are stored inside its memory and can
be transferred to a computer by
connecting the camera to it. A digital camera takes pictures by converting the light passing through
the lens at the front into a digital image.
11. Magnetic ink character recognition
(MICR)
MICR is a character-recognition technology used mainly by the banking
industry to ease the processing and clearance of cheques and other documents.
The MICR encoding called the MICR line, is at the bottom of cheques and other
vouchers and typically includes the document-type indicator, bank code, bank
account number, cheque number, cheque amount, and a control indicator. The technology
allows MICR readers to scan and read the information directly into a data-collection
device. Unlike barcodes and similar technologies, MICR characters can be read
easily by humans.
12. Joysticks
A joystick is a pointing
device often used for playing games. The joystick has a gearshift-like lever
that is used to move the pointer on the screen. In industry and manufacturing,
joysticks are used to control robots. Flight simulators and other training
simulators also use joysticks.
13. Optical Mark Readers
Optical mark
recognition, also called mark sense reader, is a technology where an OMR device
senses the presence or absence of a mark, such as pencil mark. OMR is widely
used in tests such as aptitude tests.
(d) OUTPUT DEVICES
Output
devices return processed data that is information, back to the user. Some of
the commonly used output devices are:
1.
Monitor (Visual Display Unit)
2.
Printers
3.
Plotter
4. Sound
cards and Speaker
5. Facsimile
(FAX)
1. Monitor
Monitor is the most important
output device because people interact with this device most intensively than
others. Computer information is displayed, visually with a video adapter card and
monitor. Information processed within the CPU, that needs to be visually displayed,
is sent to video adapter. The video adapter converts information from the
format used, in the same manner as a television displays information sent to it
by a cable service.
Two
basic types of monitors are used with microcomputers, which are as follows:
(a) CRT
(b) LCD
(a) Cathode
Ray Tube (CRT) - Cathode Ray Tube Monitor is the typical monitor that
you see on a desktop computer. It looks a lot like a television screen, and
works the same way. This type uses a large vacuum tube, called cathode ray tube
(CRT). The main components of a CRT terminal are the electron gun, the electron
beam controlled by an electromagnetic field and a phosphor coated display screen.
The electron gun emits an electron beam which is directed towards the phosphor
coated display by the electromagnetic field in order to create an image.
(b) Liquid
Crystal Displays (LCD) - These types of monitors are also known as flat
panel monitor. Most of these employ
liquid crystal displays (LCDs) to render images. The major advantage of LCD is
the low energy
consumption. These days LCD monitor are very popular. The CRT (Cathode Ray
Tube) is replaced by
liquid crystal to produce the image.
2. Printer
Printers are used for producing
output on paper. After a document is created on the computer,
it can be
sent to a printer for a hard copy (Printout). Some printers offer special
features such as colored
and large
page formats. Some of the most commonly used printers are:
(a) Impact
Printing
(b) Non-Impact
Printing
(a) Impact Printer – This method is used by the conventional type writers. In some type of impact printing a metal “hammer” embossed with a character strikes a print ribbon, which presses the characters image into paper.
(a) Impact Printer – This method is used by the conventional type writers. In some type of impact printing a metal “hammer” embossed with a character strikes a print ribbon, which presses the characters image into paper.
1. Dot Matrix Printer - The dot matrix
printer was very popular at one point of time. It is a very versatile and inexpensive
output device. In dot matrix printer the print head physically "hits"
the paper through the ribbon and produces text (or images) by combinations of
dots; hence the name dot matrix printer. Its speed is measured in characters
per second (CPS). Although it is less expensive, it is louder, slower and produces
lower print quality.
2. Line
Printer: A line printer is generally used with large computer systems
to produce text based data processing reports. Line printers are high-speed
printers with speeds ranging anywhere from 100 to about 3800 lines per minute.
In the past, print quality on line printers was not high.
3. Drum printer - A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface. The number of print positions across the drum equals the number available on the page. This number typically ranges from 80-132 print positions. The drum rotates at a rapid speed.
4. Daisy-wheel printers - In order to get the quality of type found on typewriters, a daisy-wheel impact printer can be used. It is called daisy-wheel printer because the print mechanism looks like a daisy; at the end of each “Petal” is a fully formed character which produces solid-line print.
3. Drum printer - A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface. The number of print positions across the drum equals the number available on the page. This number typically ranges from 80-132 print positions. The drum rotates at a rapid speed.
4. Daisy-wheel printers - In order to get the quality of type found on typewriters, a daisy-wheel impact printer can be used. It is called daisy-wheel printer because the print mechanism looks like a daisy; at the end of each “Petal” is a fully formed character which produces solid-line print.
(b) Non-Impact
Printer - It does not depend on the impact of metal on paper. In fact
no physical contact at all occurs between the printing mechanism and the paper.
The most popular non-impact methods today utilise thermal transfer.
1. Laser Printer - Laser printers are Printer that uses laser technology to print images on the paper. A laser printer produces high quality print that one normally finds in publishing. It is extremely fast and quiet. Moreover, the operation of a laser printer is easy with automatic paper loading and no smudging or messing up of ink ribbons. The fastest laser printer can print up to 200 pages per minute in monochrome (black and white) and up to 100 pages per minute in colour.
2. Ink-Jet Printer - An ink-jet printer creates an image directly on paper by spraying ink through as many as 64 tiny nozzles. Although the image it produces is not generally quite as sharp as the output of a laser printer, the quality of ink-jet images is still high. In general, ink-jet printer offers an excellent middle ground between dot matrix and laser printer.
3. Plotter
Plotters are used to print graphical output on paper. It interprets computer
commands and makes line drawings on paper using multicoloured automated pens.
It is capable of producing graphs, drawings, charts, maps etc.
4. Sound
cards and Speaker(s)
An expansion board that enables a computer to
manipulate and output sounds.
Sound cards are necessary for nearly all CD-ROMs and have become commonplace on
modern personal
computers. Sound cards enable the computer to output sound through speakers
connected to the board,
to record sound input from a microphone connected to the computer, and
manipulate sound stored on a
disk.
5. Facsimile
(FAX)
Facsimile machine, a device that can send or receive pictures
and text over a telephone line. Fax machines work by digitizing an image.
(e) COMPUTER MEMORY
Memory is used to
store data and instructions. Computer memory is the storage space in computer
where data is to be processed and instructions required for processing are
stored. The memory is divided into large number of small parts called cells.
Each location or cell has a unique address which varies from zero to memory
size minus one.
Memory
is primarily of three types
1. Primary
Memory/Main Memory
2. Cache
Memory
3.
Secondary Memory
1. Primary Memory/Main Memory
Primary
memory holds only those data and instructions on which computer is currently working. It has limited
capacity and data is lost when power is switched off. It is generally made up of semiconductor device. These
memories are not as fast as
registers. The data and instruction required to be processed reside in main memory. It is divided into two
subcategories RAM and ROM.
Two Types of Primary Memory are RAM & ROM
Two Types of Primary Memory are RAM & ROM
1. Random
Access Memory (RAM) - Random Access Memory is the unit in a computer
system. It is the place in a computer where the operating system, application
programs and the data in current use are kept temporarily so that they can be
accessed by the computer’s processor. It is said to be ‘volatile’ since its
contents are accessible only as long as the computer is on. The contents of RAM
are no more available once the computer is turned off.
The two types of RAM are Static RAM and Dynamic RAM:-
1. SRAM - SRAM retains data as long as power is provided to the memory chip and need not be refreshed periodically. SRAM stands for Static Random Access Memory.
2. DRAM - The data on DRAM continues to move in and out of the memory as long as power is available and must be continually refreshed to maintain the data. DRAM stands for Dynamic Random Access Memory.
The two types of RAM are Static RAM and Dynamic RAM:-
1. SRAM - SRAM retains data as long as power is provided to the memory chip and need not be refreshed periodically. SRAM stands for Static Random Access Memory.
2. DRAM - The data on DRAM continues to move in and out of the memory as long as power is available and must be continually refreshed to maintain the data. DRAM stands for Dynamic Random Access Memory.
2. Read
Only Memory (ROM) - Read Only Memory is a special type of memory which
can only be read and contents of which are not lost even when the computer is
switched off. It typically contains manufacturer’s instructions. Among other things,
ROM also stores an initial program called the ‘bootstrap loader’ whose function
is to start the operation of computer system once the power is turned on.
There are 4 basic ROM types:
There are 4 basic ROM types:
(a) PROM
- There is another type of primary memory in computer, which is called Programmable
Read Only Memory (PROM). You know that it is not possible to modify
or erase programs stored in ROM, but it is possible for you to store your program
in PROM chip. Once the programmers’ are written it cannot be changed and
remain intact even if power is switched off. Therefore programs or instructions
written in PROM or ROM cannot be erased or changed.
(b) EPROM
- This stands for Erasable Programmable Read Only Memory, which
overcome the problem of PROM & ROM. EPROM chip can be programmed time
and again by erasing the information stored earlier in it. Information
stored in EPROM exposing the chip for some time ultraviolet
light and it erases chip is reprogrammed using a special programming
facility. When the EPROM is in use information can only be read.
(c) EEPROM
- Electrical Erasable Programmable Read Only memory under high voltage
(d) FROM
-Flash ROM is reprogrammable memory using normal voltage inside the PC- You can
upgrade the logic capabilities by simply downloading new software. This saves
the expense of replacing circuit boards and chips.
2. Cache
Memory
The speed of CPU is extremely high compared to the access time
of main memory. Therefore, the performance of CPU decreases due to the slow
speed of main memory. The decreases the mismatch in operating speed, a small
memory chip is attached between CPU and Main memory whose access time is very
close to the processing speed of CPU. It is called CACHE memory. CACHE memories
are accessed much faster than conventional RAM. It is used to store programs or
data currently being executed or temporary data frequently used by the CPU. It
is also very expensive to have bigger size of cache memory. Its size is
therefore, normally kept small.
3. Secondary Memory
This
type of memory is also known as external memory or non-volatile. It is slower than
main memory. These are used for storing data/Information permanently. CPU
directly does not access these memories instead they are accessed via input/output
routines. Contents of secondary memories are first transferred to main memory,
and then CPU can access it.
Characteristic of Secondary Memory
Characteristic of Secondary Memory
These
are magnetic and optical memories
1.
It is known as backup memory.
2. It is non-volatile memory.
3.
Data is permanently stored even if power is switched off.
4.
It is used for storage of data in a computer.
5.
Computer may run without secondary memory.
6.
Slower than primary memories.
Types of Secondary Memory
Types of Secondary Memory
1. Magnetic
Tape - Magnetic
tapes are used for large computers like mainframe computers where large
volume of data is stored for a longer time. The cost of storing data in tapes
is inexpensive. Tapes consist of magnetic materials that
store data permanently. Magnetic tapes are used for application which requires
extremely large storage capacity where speed of access is not an issue. It is
commonly used for backups of file servers for computer networks, in a variety
of batch processing applications such as reading of bank cheques, payroll processing
and general stock control
2. Magnetic
Disk - Magnetic disks used in computer
are made on the same principle. It rotates with very high speed inside the
computer drive. Data is stored on both the surface of the
disk. Magnetic disks are most popular for direct access storage device.
Each disk consists of a number of invisible concentric circles called tracks.
Information is recorded on tracks of a disk surface in the form of
tiny magnetic spots. The presence of a magnetic spot represents one bit and its absence
represents zero bit. The information stored in a disk can be read many times
without affecting the stored data. So the reading operation is nondestructive. But
if you want to write a new data, then the existing data is erased from
the disk and new data is recorded. For Example - Floppy Disk or HDD
(a) Floppy discs - A floppy disk is a data storage medium that is composed of a
disk of thin flexible floppy magnetic storage medium encased in a rectangular plastic
shell. Floppy disks are read and written by a floppy disk drive. They had a
storage capacity of 1.4 MB. These were used to move small files such as word
processing, small spreadsheets and databases from one computer to another and
were useful to backup small data.
(b) Hard
disk drives (HDD) - Hard disk drives are used to store operating systems,
software and working data. These are
suitable for any application which requires very fast access to data for both
reading and writing to.
However, Hard disk drives may not be suitable for applications which need
portability. Almost all
computers used a fixed hard disc. Used for on-line and real time processes
requiring direct access. Used in file
servers for computer networks to store large amount of data. These may have
storage capacity
ranging from few GBs to 1 TB or more.
3. Optical
Disk - With every new application and software there is greater demand
for memory capacity. It is the necessity to store large volume of data
that has led to the development of optical disk storage medium.
Optical
disks can be divided into the following categories:
(a) Compact Disk – Compact Disk (CD) is portable disk having data storage capacity
between 650-700MB. It can hold large amount of information such as music,
full-motion videos, and text etc. CDs can be either read only or read write
type.
(b) DVD - DVDs are used to hold very large files (several GB) such as movie
films. Digital Video Disk (DVD) is similar to a CD but has larger storage
capacity and enormous clarity. Depending upon the disk type it can store
several Gigabytes of data. DVDs are primarily used to store music or movies and
can be played back on your television or the computer too. These are not
(c) CD
ROM/DVD ROM - Applications which require the prevention of deletion of
data, accidental or otherwise. CDs used by software companies for distributing
software programs and data; by Music companies for distributing music albums
and by book publishers for distributing encyclopedias, reference books etc.
DVDs used by film distributors.
(d) CD
R/DVD R - Applications which require a single ‘burning’ of data, e.g.
CDs - recording of music downloads from the Internet, recording of music from
MP3 format, recording of data for archiving or backup purposes. DVDs –
recording of film movies and television programs.
(e) CD
RW/DVD RW - Applications which require the updating of information and
ability to record over old data. Not suitable for music recording but is very
useful for keeping generations of files. DVDs have between five and ten times
the capacity of CDs.
(f) Solid
state backing storage
These are the smallest form of memory available
in the market today. Widely used
as removable storage. They are more robust than other forms of storage. Though expensive
than other forms they can be easily written to an updated. For e.g. Pen drives
& memory card or flash
memory card.
1. Memory
sticks/Pen drives - USB flash drives are typically removable and
rewritable, much smaller than a floppy disk. Storage capacities typically range
from 64 MB to 64 GB. Flash drives are widely used to transport files and backup
data from computer to computer.
2. Flash
memory cards - A memory card or flash memory card is a solid-state
electronic flash memory data storage device used with digital cameras, handheld
and Mobile computers, telephones, music players, video game consoles, and other
electronics.
2. Software
Computer
software is the set of programs that makes the hardware perform a set of tasks
in particular order.
Hardware and software are complimentary to each other. Both have to work
together to produce meaningful
results. For example, DOS, Windows 2000/2003/XP/7, Linux , MS-Office Antivirus, All games etc.
Computer software is classified into two broad categories
1.
Systems software
2.
Application Software
1. Systems software
System software consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software.
System software consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software.
There
are four main jobs an operating system is responsible for:
1.
It provides a user interface. The user interface lets you give commands to the OS.
2.
It gives instructions to the computer hardware, such as the printer and monitor.
3.
It manages the way in which the computer stores data and applications.
4.
It keeps track of different jobs. For example, if you are using both a spreadsheet
and a word processing application at the same time, the OS will run both of
these applications and let you switch back and forth between them.
2.
Applications software
Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Word processors, spreadsheets, database management systems are all examples of general purpose application software.
Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Word processors, spreadsheets, database management systems are all examples of general purpose application software.
Types
of application software are:
(a) Word
processing software: The main purpose of this software is to produce
documents. MS-Word, Word Pad, Notepad and some other text editors are some of
the examples of word processing software.
(b) Database
software: Database is a collection of related data. The purpose of this
software is to organize and manage data. The advantage of this software is that
you can change the way data is stored and displayed. MS access, dBase, FoxPro,
Paradox, and Oracle are some of the examples of database software.
(c) Spread
sheet software: The spread sheet software is used to maintain budget,
financial statements, grade sheets, and sales records. The purpose of this
software is organizing numbers. It also allows the users to perform simple or
complex calculations on the numbers entered in rows and columns. MS-Excel is
one of the example of spreadsheet software.
(d) Presentation
software: This software is used to display the information in the form
of slide show. The three main functions of presentation software is editing
that allows insertion and formatting of text, including graphics in the text
and executing the slide shows. The best example for this type of application
software is Microsoft PowerPoint.
(e) Multimedia
software: Media players and real players are the examples of multimedia
software. This software will allow the user to create audio and videos. The
different forms of multimedia software are audio converters, players, burners,
video encoders and decoders.
3. Utility software
Utility software may be considered as application software or system software which is very often used in the development of a programme. Examples of Utility softwares: WinZip, FrontPage, Notepad, Web Browsers etc
Utility software may be considered as application software or system software which is very often used in the development of a programme. Examples of Utility softwares: WinZip, FrontPage, Notepad, Web Browsers etc
Below
are some descriptions of utilities.
(a) Anti-virus applications protect your computer from the damage that can be caused
by viruses and similar programs.
(b) Compression utilities make files smaller for storage (or sending over the Internet)
and then return them to normal size.
(c) Data recovery utilities attempt to restore data and files that have been
damaged or accidentally deleted.
(d) Disk defragmenters reorganize the data stored on disks so that it is more efficiently
arranged.
(e) Firewalls prevent outsiders from accessing your computer over a network such as
the Internet.
PERIPHERAL DEVICES
Peripheral
devices are connected to the computer externally. These devices are used for
performing some specific functions.
Peripheral
devices are as follows:
1.
All Input Devices
2. All
Output Devices