Components of a Computer: The computer unit is frequently called as the computer system because of its numerous parts, machinery units and complicated sequential operation. A computer system has three main parts i.e Hardware, Software and Humanware. A general purpose computer has two main parts Hardware and Software.
Fig.
1: Block Diagram of a Computer
1.
Hardware: The physical or mechanical parts of the computer system that can
be seen and touched are known as hardware. It consists of a combination and
collection of electro-mechanical and electronic components and devices,
electronic circuits and microelectronic equipment assembled in metal boxes in
the form of modules and cabinet. All these equipment and elements are
interconnected by wiring and switching communication components like
transistors, capacitors, resistors, diodes, printed circuits, integrated
circuits, main and auxiliary storage systems, various types of magnetic media,
communication media for carrying and transformation of data, coded instruction,
etc. The different hardware parts are interconnected by busses, often made of
groups of wires.
Any
computer system has three important hardware parts. They are input device, central processing unit and the output
device. The central processing unit
itself has three parts, namely memory
unit, control unit and arithmetic and logic unit. These three
units along with the input and output devices form the five important
components of any computer system. In addition to the above five parts
mentioned, computers also have secondary
storage devices, which are used for storing data or instruction on a long
term basis.
A) Input
Unit: The input devices are
used to transfer the information into the memory unit of a computer. In
simplest term, they bring information into the computer from the user’s hand,
i.e. input unit feeds data into the computer. It is thus a communication medium
between the user and the machine. The input devices are of the following types.
i) Keyboard: Keyboards are the most commonly used
input devices usually having 83-84 keys and enhanced with 101 keys or even
more. The enhanced keyboards are more popular.
ii) Mouse: It is a hand-held pointing device that
allows controlling the computer without having to type the instruction through
keyboard. The Scrolling mouse is a small unit with a round ball at the bottom
and with two depression switches at the upper top portion having again a scroll
button. Nowadays cord less as well as without scroll ball-type of mouse is also
used.
iii)
Scanners: Scanners are used
to store or feed an entire image / data or page of other information into the
computer system. Image scanner is a general-purpose device which digitizes a
two-dimensional image.
iv) Track
Ball: A trackball is just
like a mouse lying on its back. It is stationary and does not need to move on any surface. To move the
pointer only the ball should be rotated with the thumb / finger or with the
palm. The buttons next to the ball are used just like mouse button.
v) Joystick:
A joystick is an input device consisting of a stick that pivots on a base and
reports its angle or direction to the device it is controlling. Joysticks are
often used to control video games and they usually have one or more
push-buttons whose state can also be read by the computer.
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Fig. 2:
Elements of a joystick elements: 1. Stick 2. Base 3. trigger 4. Extra buttons
5. Autofire switch 6. Throttle 7. Hat Switch (POV Hat) 8. Suction Cup
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Fig. 3: A 6×8
Wacom Intuos3 graphics tablet with DuoSwitch erasing Grip Pen stylus and
5-button scrollwheel puck.
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Fig. 4: Front
and back of a Canon PowerShot A95.
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vi)
Digitizing Tablet: A graphics tablet (or digitizing tablet, graphics pad,
drawing tablet, pen pad or digitizer) is a computer input device that allows
one to hand-draw images and graphics, similar to the way one draws images with
a pencil and paper. These tablets may also be used to capture data or
handwritten signatures.
vii) Digital
Camera: A digital camera (or digicam) is a camera that takes video or still
photographs, or both, digitally by recording images via an electronic image
sensor.
viii)
Magnetic Ink Character Recognition (MICR): It allows the computer to recognize
character printed using magnetic ink. MICR is widely used in banks to read the
cheque number written on the bottom of the cheque. It is also used in the back
of credit cards and bank debit cards and ID cards.
ix) Optical
Character Recognition (OCR): An
optical character reader is used to read character of special type fonts
printed on conventional paper with conventional ink i.e. it involves reading
text from paper, book or from a magazine articles but they still have
difficulty with handwritten text.
x) Bar Code
Reader: Bar code readers are
photoelectric scanner that reads the bar codes or vertical zebra striped marks
printed on the product container and the computer automatically tells the
prices of the product at the terminals.
xi) Speech
Recognition and Voice Response Devices: In
this type of device the user speaks into a microphone which is attached to a
digitizer. The dizitizer converts the analog sounds waves to “0” and “1”s which
can be easily understood by the computer. Speech recognition devices are
necessary because spoken commands are much quicker than typing. It helps to
give command to a remote computer over telephone. It helps the computer usable
to the blind people. In computer assisted learning environment it helps in the
interaction between the man and machine.
xii)
Touchscreen: A touchscreen is a display that can detect the presence and
location of a touch within the display area. The touchscreen has two main attributes. Firstly, it enables one to interact with
what is displayed directly on the screen, where it is displayed, rather than
indirectly with a mouse or touchpad. Secondly,
it lets one do so without requiring any intermediate device such as a stylus
that needs to be held in the hand. Such displays can be attached to computers
or, as terminals, to networks.
xiii)
Touchpad: A touchpad (also trackpad) is a pointing device consisting of
specialized surface that can translate the motion and position of a user's
fingers to a relative position on screen. They are a common feature of laptop
computers and are also used as a substitute for a computer mouse where desk
space is scarce.
xiv) 14 Light
Pen: A light pen is similar
to a mouse except that with a light pen one can move the pointer and select
objects on the display screen by directly pointing to the object with the help
of the pen.
xv) Optical
Mark Recognition (OMR): Optical
Mark Recognition (OMR) is also called mark sensing. It is a technology where an
OMR device senses the presence or absence of a mark such as pencil mark. OMR is
used in test such as aptitude test.
B) Central
Processing Unit (CPU): The
CPU is the brain of any computer system; all major calculations and comparisons
are made inside the CPU and it is also responsible for activating and
controlling the operations of other units of a computer system. It guides,
directs and controls a computer performance. It also executes the instruction
given to it. The CPU consists of the ALU, control unit, registers, and basic
I/O (and often other hardware closely linked with these). Early CPUs were
composed of many separate components but since the mid-1970s CPUs have
typically been constructed on a single integrated circuit called a
microprocessor.
a)
Arithematic and Logic Unit (ALU): The
input devices are used to transfer the information into the memory unit of a
computer. Information from the memory can be transferred to the ALU where
comparison and calculation are done and the results are sent back to the memory
unit. The set of arithmetic operations that a particular ALU supports may be
limited to adding and subtracting or might include multiplying or dividing,
trigonometry functions (sine, cosine, etc) and square roots. Some can only
operate on whole numbers (integers) whilst others use floating point to
represent real numbers with limited precision. An ALU may also compare numbers
and return boolean truth values (true or false) depending on whether one is
equal to, greater than or less than the other. Logic operations involve Boolean
logic: AND, OR, and NOT. These can be useful both for creating complicated
conditional statements and processing Boolean logic.
b) Control
Unit: It acts as a manager
which controls all activities being carried out within the computer. The
control unit strictly obeys the instruction given by us, follows the
instruction in the same sequence and executes them one after another until the
entire set of instruction is exhausted. CU brings one instruction at a time
from the memory, interprets it and obeys it by coordinating the working of all
other units. The CU tells the input unit what is to be read and addresses the
memory as to where it is to be stored. The CU ensures that according to the
stored instruction the right operation is done on the right data at the right
time. It manages and coordinates the entire computer system. The simplified
descriptions of the steps that are performed by the Control unit are given
below. Some of these steps may be performed concurrently or in a different
order depending on the type of CPU
* Read the code
for the next instruction from the cell indicated by the program counter
(program counter is conceptually just another set of memory cells, it can be
changed by calculations done in the ALU);
* Decode the
numerical code for the instruction into a set of commands or signals for each
of the other systems;
* Increment the
program counter so it points to the next instruction;
* Read whatever
data the instruction requires from cells in memory (or perhaps from an input
device). The location of this required data is typically stored within the
instruction code;
* Provide the
necessary data to an ALU or register;
* If the
instruction requires an ALU or specialized hardware to complete, instruct the
hardware to perform the requested operation;
* Write the
result from the ALU back to a memory location or to a register or perhaps an
output device
* Jump back to
step one.
c) Memory
Unit: It is the workspace
area within the computer where the data and instructions are stored. It holds
all data, instruction and results temporarily. It stores the data to be
processed, the intermediate results and the final results until they are
displayed. It contains the programs that are currently being run and the data
the programs are operating on. In modern computers, the main memory is the
electronic solid-state Random Access Memory (RAM). It
is directly connected to the CPU via a "memory bus" and a "data
bus". The arithmetic and logic unit can very quickly transfer information
between a processor register and locations in main storage, also known as a
"memory addresses". The memory bus is also called an address bus or
front side bus and both buses are high-speed digital "superhighways".
Access methods and speed are two of the fundamental technical differences
between memory and mass storage devices. Main memories are of the following
types
i) Random
Access Memory (RAM): It
is the key working area of the memory. It is possible to select randomly and
use any location of this memory. It is also called the read/write memory
because information can be read from RAM chip and can also be written into it.
It is a volatile storage medium i.e. the contents of the memory are lost when
power is switched off/cut, as it requires a steady flow of electricity to
maintain its content. RAM is also quite expensive. RAM may be of VRAM, WRAM,
NVRAM.
ii) Read
Only Memory (ROM): It
holds permanent data or instruction that can only be read. That information is
permanently recorded and cannot be changed by the programmer. It is non
volatile in nature i.e. the contents of ROM are not lost when the computer is
switched off. It contains instruction to get the computer started when the switch
is on, holds instruction and data that control the various peripheral units of
the computer such as graphic display, disk drives, etc. Most personal computers
contain a small amount of ROM that stores critical programmes, as it is
expensive to produce. Typically, ROM must also be completely erased before it
can be rewritten, making large scale use impractical, if not impossible. ROM
may be of the following types-
* Programmable
Read Only Memory (PROM): A
PROM is a memory chip on which set of instructions or information can be
stored, but it cannot be modified or wiped out later on. Like ROM its memory is
also non volatile. To write data on a PROM one will need a special device
called a PROM programmer or PROM burner. The difference between a PROM and ROM
is that PROM is manufactured as blank memory where ROM is programmed during the
manufacturing process.
* Erasable
Programmable Read Only Memory (EPROM): EPROM is used widely in personal
computers to enable the manufacturer to change the contents of PROM before the
computer is actually skipped so that the bugs can be removed and new versions
can be installed shortly before delivery. The EPROM is of two types - Electrically
Erasable PROM (EEPROM), where high voltage electric pulses are used
to erase the previous data or instruction and after that the disk can be reused
and Ultra Violet Erasable PROM (UVEPROM), which retains its data or instruction until it is exposed to
Ultra Violet light. The UV light clears its contents making it possible to
reprogramme the memory. The difference between an EPROM and PROM is that while
in PROM the data or instruction can be written only once and cannot be erased, in
EPROM the content can be erased and reprogramming can be done.
iii) Flash
Memory: Many modern PCs
have their Basic Input Output System (BIOS) stored on flash memory chip so that
it can easily be updated if necessary. Such type of BIOS is sometimes called
flash BIOS. Flash memory is also important for modem as it enables the modem
manufacturer to support new protocols as they become standardized. EEPROM is
similar to flash memory (sometimes called flash EEPROM). The principal
difference between the two is that EEPROM requires data to be written or erased
in byte at a time whereas flash memory allows data to be written or erased in
blocks. This makes flash memory faster.
iv) Cache
Memory: It is a special
type of internal memory used by many central processing units to increase their
performance or "throughput". Some of the information in the main
memory is duplicated in the cache memory, which is slightly slower but of much
greater capacity than the processor registers, and faster but much smaller than
main memory. Multi-level cache memory is also commonly used—"primary
cache" being smallest, fastest and closest to the processing device;
"secondary cache" being larger and slower, but still faster and much
smaller than main memory.
C) Output
Unit: An output device is any
product or machine that is capable of bringing information for user view. It
presents the processed data or information to the user. It can be a printed
page, a picture in monitor, and so on. Anything which comes out of a computer
system is the output of it. The common output devices are-
a) Monitor
[Video Display Unit (VDU) / Cathode Ray Tube (CRT)]: It looks like a television. The
advantage of having a video display unit is that as we write we can see what is
being fed into the computer and by this way we can spot the mistakes and make
the necessary correction. It also helps to display the stored information
inside the computer system.
b) Liquid
Crystal Display (LCD): CRT
screens are relatively heavy and bulky, therefore unsuitable for small portable
computer like note book. Considering this the screen of a portable computer is effectively
replaced by a flat panel LCD screen which is smaller in size and lighter in
weight.
c) Printer: A computer printer, or more
commonly called the printer, is a device that produces a hard copy (permanent
human-readable text and/or graphics) of documents stored in electronic form,
usually on physical print media such as paper or transparencies. Many printers
are primarily used as computer peripherals, and are permanently attached by a
printer cable to a computer which serves as a document source. The latest
technology is combining printers with a scanner and/or fax machine in a single
unit. The world's first computer printer was a 19th-century mechanically driven
apparatus invented by Charles Babbage for his Difference Engine.
d) Plotter: A plotter is a vector graphics
printing device which operates by moving a pen over the surface of paper.
Plotters are used in applications such as computer-aided design, though they
are being replaced with wide-format conventional printers.
e) Speaker: Speaker output the music or speech
from the programme. A speaker or loudspeaker converts an electrical signal to
sound. The speaker pushes a medium in accord with the pulsations of an
electrical signal, thus causing sound waves to propagate to where they can then
be received by the ear.
f) Computer
Output on Microfilm and Microfiche (COM): The
output from the computer, instead of being printed is displayed on a high
resolution cathode ray tube, and the output is obtained in microfilm or
microfiche from which it is often used to store massive data in compact form. Then,
when needed, with the help of a special microfilm reader it is used to read the
output.
g) Speech
Output Unit: A speech
output unit is one which reads string of character stored in a computer memory
and converts it into spoken sentence. This type of speech output is very useful
in many areas.
Examples: A
telephone where a message is given to the caller when the number dialed does
not exist, railway and airlines enquires.
D) Auxiliary Storage Devices: Auxiliary memory / storage devices or
secondary storage supplements the main memory and it requires the computer to
use its input/output channels to access the information. Secondary storage is
also known as “mass storage devices”. It functions as back up device even if by
some accident the computer is crashed and the data in it is unrecoverable. One
can restore it from the backups. It acts both as input and output devices. The
secondary storage devices are also used as a transport medium to transfer data
or information from one computer system to another computer system. If we use
keyboard as an input device we will waste a lot of valuable computer times
because manual input is always slow. Secondary storage is also used for
long-term storage of persistent information. Secondary
storage device includes Magnetic tapes, Floppy disc, CD / DVD, Pen drive,
External Hard Disc etc. The Floppy and Magnetic Tapes are now obsolete as
secondary storage devices.
i)
CD-ROM: CD-ROM is an abbreviation
for Compact Disc Read-only memory. The standard CD-ROM holds 650 or 700
MiB of data. A "700 MB" CD has a nominal capacity of about 700 MiB.
The CD-ROM is popular for distribution of software, especially multimedia
applications, and large databases.
ii)
DVD: It typically may contain
at least 4.4 GiB of data, nearly 7 times the amount of a CD-ROM. DVD capacities
are given in decimal units: A "4.7 GB" DVD has a nominal capacity of
about 4.38 GiB.
iii)
Pen Drive: A USB flash drive consists of a NAND-type flash memory data
storage device integrated with a USB (Universal Serial Bus) interface. USB
flash drives are typically removable and rewritable, much smaller than a floppy
disk, and most weigh less than an ounce (30 g). Storage capacities can range
from 64 MB to 256 GB with steady improvements in size and price per capacity.
Some allow 1 million write or erase cycles and have 10-year data retention,
connected by USB 1.1 or USB 2.0.
2.
Software: A computer cannot perform on its own. It needs to be exclusively
instructed on what it has to do, the programmes written for a computer to
perform different operation are called software and it can be defined as ‘the
set of computer programme, procedures and associated documentation or complete
set of instruction which enable the computer to obtain solution of a problem
that resides in the memory or storage device of a computer’. (The programme is
a set of instructions written in computer language). Software is a general term
that is used to describe only single programme or group of programme and makes
the hardware run. It acts as an interface between the user and the computer.
Computer softwares are generally classified into two broad categories:
A) System
Software: It is a set of one
or more programs, designed to control the operation of a computer system.
Generally, the system software supports the running of the other software,
communicates with other peripherals devices, supports the development of other
types of software and supervises the user of various hardware resources. System
software is of the following types-
a) Operating
System: An operating system
(OS) is an integrated set of computer programmes that manage the hardware and
software resources and the overall operation of a computer system. The
operating system is designed to support the activities of computer
installation. It acts as an interface between a user and the hardware i.e. all
computer resources. It forms a platform for other system software and for
application software. Its prime objectives are to improve the performance and
efficiency of a computer system, increase the facility and the ease with which
a system can be used. Most operating systems have a command line interpreter as
a basic user interface, but they may also provide a Graphical User Interface
(GUI) for ease of operation. Operating systems are mainly of two types-
i)
Command / Character User Interface (CUI): In this type of OS the user has
to type the commands at the command prompt mode, which will act as an input to
execute and program. E.g. UNIX, MS DOS.
ii) Graphic User Interface (GUI): In
this type the user is able to select files, programmes or commands by pointing
to graphical representations on the screen and thereby it avoids the typing of
lengthy complex commands. E.g. Windows XP.
b) Language
Processor: Men use their own
language (High Level Language) to write their programmes because it is much
easier to code in such languages. However, the computer is unable to understand
such a High Level Language; it only understands its own language i.e. Machine Language
(Binary Language). Therefore, it becomes necessary to process a HLL to LLL. The
computer programme that performs this job is the language processor. The
language processors are of the following types-
i) Assembler: In the 1950s to reduce programming
complexity in Machine Language and to provide some standardization, assembly
languages were developed. Assembly language is also known as Symbolic Language.
Assembly language uses abbreviation or mnemonic code to replace the earlier 0s
and 1s of machine language. i.e. it substitutes letters and symbols for the
numbers in the machine language program. The function of an assembler is to
translate an assembly code into the computer machine code / language.
ii)
Interpreter: This language
processor converts a HLL program into machine language by converting and
executing it line by line. If there is any error in any line, it reports it at
the same time and the programme execution cannot resume until the error is
rectified. For error debugging the interpreter is very useful as it reports the
errors at the same time, but, once errors are removed then also interpreter is present
in the memory. So, unnecessary usage of memory takes place in this case.
iii)
Compiler: It converts the
entire HLL program at one go and reports all the errors of the programme along
with the line numbers. After all the errors are removed, the programme is
recompiled and after that the compiler is not needed in the memory as the
object programme is available.
a) Packages: The application softwares that are
designed for the individual user, so that they can be used in a manner that
suits their needs and requirements are known as packages. Actually it is a
bundle of essential features for carrying out a particular task. There are
different packages available in the market. Some of the most common categories
are given bellow-
i) Word
Processing Software: It is the
software that processes textual matter and creates organized and flawless
documents. It provides a general set of tools for entering, editing and
formatting text. A word processor has everything that a conventional type
writer has; in addition, it also removes various barriers of the conventional
type writers. eg. M.S. Word, Wordstar, WordPerfect, Softword, etc.
ii)
Spreadsheet: An electronic
spreadsheet is a programme that accepts data values in tabular form and allows the
users to manipulate / calculate / analyze data in the desired manner. It can also
generate graphs and charts to show the relationship among numbers. Eg. MS
Excel, Quattropro, etc.
iii) Database
Management System: A DBMS is a
software that can effectively store, manipulate and handle bulk of data. Eg.
Foxpro, MS Access, Oracle, etc.
iv) Desktop Publishing Software: Desktop publishing packages handle page layout by combining the function of a traditional typesetter and a layout artist.
iv) Desktop Publishing Software: Desktop publishing packages handle page layout by combining the function of a traditional typesetter and a layout artist.
v) Graphics: The application software that
manipulates images is known as graphics software.
vi)
Multimedia: The software that
incorporates images, text, sounds, animation, video sequences is known as
multimedia software.
vii)
Presentation Software: The
application software that concentrates on professional looking visual aids is
called presentation graphics software. Eg. Corel Draw, Macro Media, Director,
MS. Power Point, etc.
b) Utilities
Software: Utility software (also known as service program, service routine,
tool, or utility routine) is a computer software designed to help, manage and
tune the computer hardware, operating system or application software by
performing a single task or a small range of tasks. Some utility softwares have
been integrated into most major operating systems.
i) Text Editors: Text and Hex / Editors
directly modify the text or data of a file. These files could be data or an
actual programme.
ii) Backup Utility: Backup utilities can
make a copy of all the information stored on a disk, and restore either the
entire disk (e.g. in the event of disk failure) or selected files (e.g. in the event
of accidental deletion).
iii) Compression Utility: Disk
compression utilities can transparently compress / uncompress the contents of a
disk, increasing the capacity of the disk.
iv) Disk Defragmenter: Disk
defragmenters can detect computer files whose contents are stored on the hard
disk in disjointed fragments, and move the fragments together to increase
efficiency.
v) Antivirus Software: Anti-virus
utilities scan for computer viruses.
c) Customized
Software: Customized software (also known as Bespoke software) is a type of
software that is developed either for a specific organization or function that
differs from or is opposite of other already available softwares (also called
off-the-shelf or COTSsoftware). It is generally not targeted to the mass
market, but is usually created for companies, business entities, and
organizations.
The
trained computer professionals who, by their knowledge are able to run the
computer and can perform different operations are known as Humanware. They are
the persons who programme, design and operate a computer installation such as
System Analyst, Programmer and computer operator
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https://www.youtube.com/watch?v=owZeCkfMas8
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https://www.youtube.com/watch?v=Lj0m3Bf8D5A
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https://www.youtube.com/watch?v=UOuqF5DcEUw
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https://www.youtube.com/watch?v=PDb46OwJESs
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https://www.youtube.com/watch?v=34fYjBW_L0M
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https://www.youtube.com/watch?v=lCc8lY8PpjU
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