Unit 1 Computer system

1.1 Introduction of computer

1.1.1 Definition, characteristics and application of computer
1.1.2 Evolution of computer technology
1.1.3 Measurement unit of processing speed and storage unit
1.1.4 Super, Mainframe, Mini and Microcomputers
1.1.5 Mobile Computing and its Application

1.2 Computer system and I/O devices

1.2.1 Concept of computer architecture and organization
1.2.2 Components of computer system: input unit, output unit, processing unit,
memory unit and storage
1.2.3 Microprocessor: basic concepts, clock speed, word length, components and
functions
1.2.4 Bus System: data bus, address bus and control bus
1.2.5 Primary memory: Definition, RAM, ROM, Cache, Buffer, types of RAM and ROM
1.2.6 Secondary Memory: Definition, Magnetic Disk, Flash Memory, Optical
Disk, External Storage Device and memo stick
1.2.7 Input Devices – Keyboard, Mouse, Scanner, Light Pen, OMR, OCR, BCR, MICR,
Scanner, Touch Screen, Microphone and Digital Camera.
1.2.8 Output Devices: Monitor (LCD, LED), Printer (Dot Matrix, Inkjet, Laser), Speaker
1.2.9 Hardware Interfaces: Parallel Port, Serial Port, USB Ports, HDMI and
Expansion Slots
 1.1 Introduction of computer
Q. what is computer? Draw a block diagram of computer.
Ans: The full form of COMPUTER is Common Operating Machine Particularly
Used for Trade, Education and Research. Technically speaking, the term
computer does not have a full form. A computer is an electronic and
automated machine that accepts raw data, process it and display meaningful
information or result. The term ‘computer’ originates from the word
‘computare’ which means ‘to calculate’.

Fig. Block diagram of Digital computer

 •Input unit: The unit that converts human understandable form into machine
language or binary language (0 or 1) is called input unit.
•Process unit: The unit that performs some action on data and produce
meaningful output or information or result.
•Output unit: the unit that converts machine language or binary language
into human understandable form is called output unit.
•Data: Data refers to raw, facts and figures.
•Information: Processed data is called information.

. What are the features of computer? Explain each.

ns: The features of computer are as follows:
Speed: As you know, computer can work very fast. It takes only few seconds
or calculation that we take hours to complete. We determine the speed of
omputer in terms of millisecond, microsecond, nanosecond, picoseconds etc.
he speed of computer is measured in Hertz (Hz).
Units of time Part of second Power of 10

Millisecond or 10 -3

Microsecond or 10 -6

Nanosecond or 10 -9

Pico second or 10 -12

Femto Second or 10 -15

b. Accuracy (correctness): - The degree (amount) of accuracy of

computer is very high and every calculation is performed with the same
accuracy. The accuracy level is determined on the basis of design of
computer. The errors in computer are due to human and inaccurate data.
c. Diligence: - A computer is free from tiredness, lack of concentration,
fatigue (low energy), etc. It can work for hours without creating any
error. If millions of calculations are to be performed, a computer will
perform every calculation with the same accuracy.
d. Versatility: - It means the capacity to perform completely different
type of work. You may use your computer to prepare payroll slips.
Next moment you may use it for inventory management or to prepare
electric bills.
e. Power of Remembering: - Computer has the power of storing any
amount of information or data. Any information can be stored and
recalled as long as you require it, for any numbers of years. It depends
entirely upon you how much data you want to store in a computer and
when to lose or retrieve (get back) these data.

f. No Feeling: - It does not have feelings or emotion, taste, knowledge

and experience. Thus it does not get tired even after long hours of work.
It does not distinguish between users.

g. Storage: - The Computer has an in-built memory where it can store

a large amount of data. You can also store data in secondary
storage devices such as floppies or pen drive, which can be kept
outside your computer and can be carried to other computers.
0 or 1 =1 Bit
4 Bits = 1 Nibble
8 Bits = 1 Byte
1024 Bytes = 1 KB (Kilo Byte)
1024 KB = 1 MB (Mega Byte)
1024 MB = 1 GB (Giga Byte)
1024 GB = 1 TB (Tera Byte)
1024 TB = 1 PB ( Peta Byte)
1024 PT = 1 EB (Exa Byte)
1024 EB = 1 ZB (Zetta Byte)
1024 ZB = 1 YB (Yotta Byte)
1024 YB = 1BB (Bronto Byte)
1024 BB = 1 GeB (Geop Byte)
Q. what are the application areas/fields of computer.
Ans: The application areas of computer are:
1. Businesses:
Businessmen make bar graphs and pie charts from tedious (boring) figures to
convey information. Furthermore, computers help businesses to predict
(guess) their future sales, profits, costs etc. making companies more accurate
in their accounts.

2. Buildings:
Architects use computer animated graphics to experiment with possible
exteriors and to give clients a visual walk-through of their proposed
buildings. The computers provide architects numerous amounts of facilities
to create different buildings with greater accuracy, better designing,
editing tools and work done at the fastest speed possible.
3. Education:
Most good schools in the world have computers available for use in the
classroom. It has been proved that learning with computers has been more
successful and this is why numerous forms of new teaching methods have
been introduced. This enhances the knowledge of the student at a much
faster than the old traditional methods.

4. Transportation:
Computers are used in cars to monitor fluid (liquid) levels, temperatures and
electrical systems. Computers are also used to load containerships across the
country. An important part is the air control traffic systems, where computers
are used to control the flow of traffic between airplanes which needs a lot of
precision (correct) and accuracy to be deal with.
5. Government:
Among other tasks, the federal (central) government uses computers to
forecast the weather, to manage parks and historical sites, to process
immigrants, to produce social security checks and to collect taxes. The most
important use of the computer system in this field is perhaps the Army, the
Air Force and the Navy (ship army). The computers have to be very powerful
and in order to be run they have to be very accurate and precise.

6. The Home:
A person having a computer in the home justifies the fact that it is not only
useful and efficient, but it is also honored as a learning system. Personal
computers are being used for numerous tasks nowadays, for example, to keep
records, write letters and memos, prepare budgets, produce presentations,
draw pictures, publish newsletters and most importantly - connect with other
in the rest of planet (earth).
7.Communication with the World:
The computes are most popular for their uses to connect with others on the
World Wide Web. Emailing, teleconferencing and the use of voice messages
are very fast, effective and surprisingly cheaper as well. When connected to
the Internet, people can gain various amounts of knowledge and know about
world events as they occur. Purchasing on the internet is also becoming very
popular and has numerous advantages over the traditional shopping methods.

8. Training:
It is much cheaper and effective to teach pilots how to fly in a computerized
cockpit or simulators, than in real airplanes. This is because the learning pilots
will feel much more relaxed and confident due to the fact that no life is at risk
at that moment. Railway engineers can also be given some kind of training on
how to run a train with the help of a computerized system.
9.Health and Medicine:
10.Manufacturing Industries:
 History of Computer/ Evolution of Computer
Q. List the early development of computer era.
Ans: The early developments of computer era are as follows:
) Mechanical Era (Zeroth generation) 500BC-1890 AD: The calculator of this
age was developed by using mechanical components like wood, metal, stone,
bone, etc. It was used for simple mathematical calculations. E.g. Abacus,
Slide Rule, Napier’s Bone, Pascaline, Jacquard’s Loom, Stepped Reckoner,
Difference Engine, Analytical Engine.
. Electro-mechanical Era-1891-1945: The calculator of this age was developed
by using mechanical and electronic component vacuum tube. E.g. Mark-I, ABC,
Tabulating Machine etc.
i. Electronic Era-1946-today: The calculator of this age was developed by
using electronic component vacuum tube. E.g. ENIAC, EDSAC, EDVAC, UNIVAC etc.
Q. what is an Abacus?
Ans: In ancient period, it was used to calculate mathematical calculation. It was
used for performing simple calculation like counting, addition, subtraction and
multiplication of number. An abacus consists of a rectangular frame carrying a
number of wooden rods. Mid-bar divides each of these rods – upper and lower
parts. The upper part is called heaven whereas lower part is called earth. The
heaven consists of two beads, whereas the earth part consists of five beads to
each rod. The value of bead on heaven part is five and earth is one. Each
abacus consists of nine or eleven or thirteen rods. Abacus is also know as
“Soroban”.

Fig. Abacus
 Q.2. Write short notes on.
i.Napier bone: The Scottish mathematician John Napier first
published the table of logarithms in 1614 AD. It was very used and
consists of a large number of calculations. He invented bone rods and
used bones to demonstrate by subtracting and multiplication by addition
according to his principle. These are made of strips of bones on which
numbers were fixed and painted that`s why it is also called Napier's bone.
It is also known as Cardboard multiplication calculator.
ii. Slide Rule (Oughtred Rule): An English mathematician William
Oughtred invented slide rule in 1620 A.D. It is a rectangular device-
slide-rule. It was a calculating device based on the principle of a log.
A rule consists of two graduated scales, one of which slips upon other.
It is devised in such a way that suitable alignment of one scale against
the other makes it possible to find products and quotient of any numbers.

Fig. Slide Rule

iii. Pascal Calculator(Pascaline) : The man name Blaise Pascal, was a brilliant
mathematician and religious thinker. Pascal made a mercury barometer and
measured atmospheric pressure to assist his father in his work accounting.
Pascal invented the first mechanical calculation machine in Paris.
 Fig. Pascaline

iv. Stepped Reckoner:In 1671, Baron (Tycoon) Gottfried Wilhelm Von Leibniz
develops a new method of calculation called 'Calculus'. He modified the
pascaline machine and invented a first calculator, Stepped Reckoner, which was
able to perform automatic addition, subtraction, multiplication, division, but
could find out square root. Each with nine teeth of varying lengths instead of
wheels it was called 'Leibniz Calculator' or 'Stepped Reckoner'.

Fig. 'Leibniz Calculator'

v. Joseph Marie Jacquard (Jacquard loom) : The French man, Joseph Marie
Jacquard, was a textile manufacturer who invented a mechanism for automated
weaving clothes for the textile industry at Lyon, in 1802 AD. This machine was
used to automatically control weaving looms to facilitate the production of
weaving cloth with complex patterns.

Fig. Jacquard loom

vi. Calculating device of Charles Xaiver : In 1820, a Scientist of France , Charles

Xavier invented a calculating machine that could perform simple arithmetic
Calculation such as addition, sub, mul and division. This calculating machine
was named as Arithmometer.
 Fig. Arithmometer

vii. Difference Engine :In 1822, English mathematician Charles Babbage, at

Cambridge University, UK, proposed calculating machine having the size of
room, which he called the Difference Engine. This machine was able to
compute tables of numbers, such as logarithm tables. Ten years Later the
device was still nowhere near complete and funding dried up. The device
was never finished.
 Fig. Difference Engine Fig. Analytical engine

viii. Analytical engine: The English Professor and Mathematician, Charles

Babbage, invented the Analytical Engine at Cambridge University, in 1833 AD.
Analytical enghine had several features including inputting data, storing
information, performing arithmetic calculation and printing out result which
are also found in modern electronic computer. Analytical engine provided the
foundation for modern computer. Therefore, Charles Babbage I known as
“ father of modern computer “.
ix. Lady Augusta Ada Byron Lovelace: The English intelligent and
independent-minded woman, Lady Augusta, was a daughter of English poet
Lord Byron and a very Great follower (fan), assistant of Charles Babbage.
Lady documents Babbage`s work and writes programs for Babbage. His plan is
now regarded as the first computer program. That`s why, she was considered
the first computer programmer & Ada is a programming language somewhat
similar to Pascal, was named Ada in her honor.
x. Dr. Herman Hollerith : An American Inventor, Herman Hollerith, also
applied the Jacquard loom concept in computing and applies for patents (law)
for an automatic punch-card tabulating machine. He invented a machine knows
as “Tabulating Machine ". This device could process on the punch cards and
perform census calculating faster than ever before.

xi. John Von Neumann : The Hungarian Mathematician, John gave an idea of
stored program computer in the sense that program is stored internally in the
main memory of the computer along with its associated data, in 1945. So, he is
called the "Father of Stored Program". Before that, program required for the
computer were included and written permanently in chips. So, modification of
program was not possible. But, after Neumann, such programs were stored on
a computer in some storage media, so modification was easy and flexible.
 John Von Neumann

xii. The Atanasoff -Berry Computer: ABC was the world’s first electronic digital
computer. In 1939, John Vincent Atanasoff and Clifford Berry designed
Atanasoff -Berry computer. It used 18000 valves and other 45 valves for
internal logic and capacitors for storage. It used punch cards as input and
output operation. It is considered as the first computing machine which
introduced the idea of binary arithmetic, regenerative memory and
logic circuits.
 Atanasoff -Berry Computer

xiii. The Mark I Computer/ASCC: A Professor of Physics, Howard H. Aiken

designed a general purpose mechanical computer at Harvard University and
IBM Automatic Sequence Controlled Calculator (IBM ASCC). It was the first fully
automatic calculating machine and later as Harvard Mark I. It used binary
numbers for its operation. Later, Mark II was invented by Aiken and his
colleagues that were working electromechanical relays for its operation.
Mark II used 19000 valves.
 The Mark I Computer/ASCC

xiv.Boolean Algebra Boolean Algebra is the branch of mathematics that deals

with logical calculation. In this algebra, binary decision are manipulated where
1 stands for true or ON or presence or high and 0 stands fro false or OFF or
absence or low. Boolean Algebra was invented by George Boole in 1854 A.D.
xv. ENIAC: In 1946, John W. Mauchly and J.presper Eckert constructed ENIAC
(Electronic Numerical Integrated and Calculator), at the Moore School of
Engineering of the University of Pennsylvania, USA. ENIAC was the first popular
generals purpose all electronic digital computers. John Von Neumann was the
consultant of the ENIAC project. It was a very large machine weighing about
30 tons and containing about 17,468 vacuum tubes, 70,000 resistors, and it
consumed 160 kilowatts.

EDVAC

xvi. EDVAC: EDVAC (Electronic Discrete Variable Automatic Computer) was

developed by Dr. John Von Neumann and a member of the Moore School of
Engineering of the University of Pennsylvania (k]g]zLNeflgo_, J.P Eckert, and
J.W Mauchly in 1952 A.D. The EDVAC is used for Moore school personnel (staffs)
and the Ballistics Research Laboratory of the US Army, which was based on
John Von Neumann`s ideas of Stored Program".
xvii. EDSAC: EDSAC (Electronic Delay Storage Automatic Computer) was designed
by Maurice Wilkes at Cambridge University in 1947 A.D. it contains 3000
vacuum tubes and operated on 30KW. The time required for addition was
1500 microsecond, for multiplication 4000 microsecond.

EDSAC UNIVAC

xviii. UNIVAC: UNIVAC (Universal Automatic Computer) was developed by

J.P.Eckert and J. Mauchly in 1951. It was the first computer manufactured for
commercial use and general purpose digital computer. It was designed to
handle both numeric and textual information. It was 8 feet height, 15 feet long
and weight was about 15 tones.
Q. what do you mean by generation of computer? How many computer
generations are there?
Ans: The development of computer in different time period is known as
computer generation.
There are five computer generations. They are:
•First Generation Computer (1946-1956)
•Second Generation Computer (1957-1965)
•Third Generation Computer (1966-1973)
•Fourth Generation Computer (1974- 2020)
•Fifth Generation Computer (2020 and future)
Q. Write down the features/ characteristics of 1st, 2nd, 3rd, 4th and 5th
generation of computer.
Ans: The features of first generation computer are:
•Technology used: vacuum tube
•Machines languages were used to instruct the computer.
•Magnetic core memory was used as primary memory.
•Punched card, printing devices were used for input/output operations and
store the result.
•It occupies very large space, slow processing, inefficient and unreliable due
to low accuracy.
•Power consumption was very high and it generated much heat.
•It could only perform straight forward simple numerical calculation.
•Computer used to be much expensive.
The features of second generation computer are:
•Technology used: Transistor
•Operating speed was in terms of a microsecond.
•Assembly language and machines independent language such as COBOL
(Common Business Oriented Language) and FORTRAN (Formula Translation)
were introduced the size of the computer.
•Magnetic core memory was used as primary memory.
•Magnetic drum and magnetic tape were used as secondary memory.
•It could perform scientific calculation such as solving differential equations.
•Storage capacity and use of computers are increased.
The features of third generation computer are:
•The technology used: IC (Integrated Circuit).
•Transistors were replaced by IC in their electronic circuitry.
•High-level languages like FORTAN, BASIC and other are used to develop
programs.
•Semiconductor memory like RAM and ROM were used as primary memory.
•Monitor and keyboard were introduced for data input and output respectively.
•Multiprogramming facility was developed.
•The computer was used in census calculation, military, banks and industries.
•Size, cost, power requirement and heat generation decreased.
•Processing speed and storage capacity used of computer increased.
The features of fourth generation computer are:
•Technology in use: VLSI (Very Large Scale Integration) is introduced and
used Microprocessor-based technology.
•Problem-oriented fourth generation language (4GL) is used to develop
the program.
•Semiconductor like RAM, ROM and cache memory is used as a primary
memory.
•Magnetic disks like hard disk, optical disk (CD, DVD), Blue-ray disk, flashes
memory (memory chip, pen drive) are used as secondary memory.
•E-mail, Internet and mobile communication are developed.
•Advanced, user-friendly, web page software are developed.
•Size, cost, power requirement, heat generation decreased compared to the
previous generation.
•Operating speed, storage capacity ,use of computer increased compared to
the previous generation
The features of fifth generation computer are:
•Technology to be used: These machines will incorporate Bio-chip and
VVLSI (Very Very Large Scale Integration) or Ultra-Large Scale Integration (ULSI)
•The computer will have Artificial Intelligence (AI).
•Natural language will be used to develop programs.
•The computer will have parallel processing in full fledge.
•The operating speed will be in terms Femto per second or of LIPS(Logical
Inference per Second)
•This aim is to solve highly complex problems, which require great intelligence
and knowledge when solved by people.
voice recognition, visual recognition. robots

EG:
IBM notebooks.
SUN Workstations
IBM SP/2
PARAM supercomputers.
Q.5 How is Computer Speed Measured?
Ans: Computer speed and its measurement can be taken in different ways:
 Bit width: The first way of describing a processor is to say how many bits
it processes in a single instruction across the processor's internal bus in a single
cycle. Current chip designs are 64 bit chips (as of 2008). More bits usually
mean more processing capability and more speed.
•Clock Cycles: The second way of describing a processor is to say how many
cycles per second the chip operates at. This is how many times per second a
charge of electricity passes through the chip. The more cycles, the faster
the processor.
 Execution cores: The third way of describing a processor is to say how many
execution cores are in the chip. The most advanced chips today have
(dual core processor have two core, quad-core processor have 4 cores
i.e i3, i5 or i7 or hexa-core processor have 6 cores) eight execution cores.
More execution cores means you can get more work done at the same time,
but it doesn't necessarily mean a single program will run fast.
 CPU speed measurement: The main measurement passage by manufacturers
as a supposed indication of processing speed is the clock speed of the chip
measured in Hertz (Hz). The theory goes that the higher the number of mega
or giga hertz, the faster the processor. Counting how many instructions are
processed per second (MIPS- Millions or BIPS-Billions or
TIPS- Trillion of instruction per second) is better measurement.
 Classification of Computer
Q. Classify the computer on the basis of size/volume. Explain them.
Ans: On the basis of their capacities and uses computers are classified as follows
i. Super computer
ii. Mainframe computer
iii. Mini computer
iv. Micro computer

Super: Super computers are mainly designed for complex and high volume
ocessing requirements. They are the most powerful and expensive computers.
ey are used for animated graphics, weather forecasting, weapon plasma etc.
g. CRAY-I, NEL-500 etc.
ii. Mainframe: These computers are mainly designed for centralized data
processing activity within the organization. Those types of computers are
medium-large in size. It is powerful and multiuser computer that can be used
in large business organization, industries and governmental sector.
E.g. IBM 1401, ICL 2859/10 etc.
iii. Mini: Minicomputer is a general purpose computer which is comparatively
smaller and less expensive than a mainframe computer. They are generally
applied to perform smaller work in commercial and government organization.
E.g. VAX, PDP-8 etc.
iv. Microcomputer: A micro computer is the smallest general purpose data
processing system. They contain small CPU, normally called microprocessor.
They are easy to handle and are use in different application areas like business,
education, entertainment, hospital etc. Desktop computers, laptops, tablet PCs,
and many types of handheld devices, including mobile phones, pocket
calculators etc. Microcomputers are further divided into following categories:
•Laptop computer
•Note book
•Palmtop
•Handheld computer Cellular telephones
Q. What do you mean by mobile computing? Explain
Ans: Mobile Computing is a technology that allows transmission of data,
voice and video via a computer or any other wireless enabled device
without having to be connected to a fixed physical link. Many types of
mobile computers have been introduced since the 1990s. The main
concept involves −Mobile communication, Mobile hardware and Mobile
software. Mobile hardware includes portable laptops, Smartphone’s,
tablet Pc's, Personal Digital Assistants, notebook PCs and other
handheld devices. Mobile software is the actual program that runs on
the mobile hardware. This is the engine of the mobile device. Mobile
devices can be connected to a local area network (LAN), or they can
take advantage of Wi-Fi (Wireless-Fidelity) or wireless technology by
connecting via a wireless local area network (WLAN). Wi-Fi is commonly
used in public places like airport terminals, hotel lounge, offices, etc.
Q What are the features/merits (Pros) of Mobile computing?
Ans: The features of mobile computing are:
1. Easy to handle and carry these small devices.
2. Data can be transferred easily between users.
3. Having fast processor speed.
4. Huge memory capacity.
5. No time restriction.
6. No place restriction.
7. Reduce cost and time.
Q What are the application areas of Mobile computing?
Ans: The application of mobile computing are:
1. Traffic control & information
2. Use in business
3. Credit card verification
4. Entertainment
5. Banking
6. Medical
7. News reporting
8. Education etc.
Q. What are merits and demerits of Mobile computing?
Ans: The demerits (Cons) are:
•Connectivity issues: To complete their tasks, employees need network
connectivity. Unless the workers have a reliable connection, they will not be
able to access the information they need to effectively function in their
respective roles.
•Power consumption: Mobile devices, especially the commercial ones do not
have enough power to last an entire day. Unless there are chargers and power
sources, an employee might not be able to complete his tasks.
•Security concerns. This is the biggest concern most people have over take on
mobile solutions. Because employees would have to connect over a wireless
network in order to access company data, it leaves the network level to
hackers who might steal sensitive company information.
 1.2 Computer system and I/O devices
Q. Define computer architecture and computer organization.
Ans: Computer architecture is the study of the components/parts that make up
computer systems and how they interconnect.
Computer organization is concerned with the implementation of computer
Architecture.

Q. Briefly explain the architecture layer of computer.

Ans: The architecture layer of computer are:

7 Application
6 Software Level High order S/w layer
5 OS Layer

4 Machine Layer
3 Hardware Level Microprogramming Layer
2 Digital Logic Layer
1 Physical device Layer
 Physical Device Layer(1st Level): It consists of electrical (power supply) and
ectronic components such as transistor, capacitors and register. It is
sponsible for the actual physical connection between the devices.
he physical layer contains information in the form of bits and these bits are
nd to upper layer digital logic layer.

Digital Logic Layer: It can store , manipulate(work) and transmit data in the
rm of simple binary representation forming frame and send towards
icroprogramming layer. Digital logic elements are called gates.

Microprogramming Layer: It interpret/read/take the binary language

nstruction from the machine layer and directly caused the digital logic
ements to perform the required operation. Likewise sends towards the
achine layer as a packet routing.
Machine Layer: It Is the level at which program can be written and
ally it is only machine language instruction, which can be directly
erpreted by hardware.

OS layer: It controls the way in which all software uses the underlying
rdware. It also hides the complexities of the hardware from other
oftware by providing its own facilities, which enable software to use
e hardware more simply.

Higher order S/w Layer: It covers all program in language other than
achine language, which require translation on to machine code before
ey can be executed.

Application Layer: It is the language of the computer as seen by the

d user. It is the layer where we used to communicate with the system.
Q. Define computer system.
Ans: The different parts of the computer connected to the CPU for smooth
operation is called computer system.

Q. Draw block diagram of a digital computer and explain its hardware

components briefly.
Ans: The different hardware components are described below:
Fig. block diagram of a digital computer
i. Input unit
ii. Output unit
iii. Processing unit (CPU)
iv. Memory Unit (storage unit).

i. Input Unit: It accepts the data or instruction given by the user and it
converts data or instruction from man-readable form to machine
readable code. E.g. input devices are mouse, keyboard ,OCR etc.

ii. Processing Unit/ CPU: CPU is a portion of a computer system that

carries out the instruction of the computer program and it is the
main element carrying out the computer function. CPU is a major
component of any computer . It acts as the heart and brain of
computer and perform all the processing related activities.
Therefore, the processing unit is popularly known as CPU (Central
Processing Unit). CPU performs the following function:
a) It performs all the calculation.
b) It takes all the decisions.
c) It controls all units of the computer.
Some of the main components of the CPU or processor are given
below:
1. Register array
2. CU (Control Unit)
3. ALU (Arithmetic and Logic Unit)

1. Register array : Register are the main memory of the computer

system. They are mainly used to store data during the time of
processing inside ALU .
Features of register:
• They are the fastest memory of the computer.
• The storage capacity of register is small.
• They are temporary memory of computer.

Processor
2. Control Unit (CU): The control unit carries out the controlling
operation of computer. It performs data processing operation. It
sends control signal to the various parts of the computer system for
the purpose of controlling. It gives command to input data from input
unit to memory unit to ALU.
3. ALU (Arithmetic and Logic Unit): It contains electronic circuits
necessary to perform all the arithmetic and logical operation. All the
calculations are performed in the ALU of the computer. The
arithmetic operation includes addition, subtraction, multiplication etc.
and logical operation includes AND, OR NOT etc.
iii. Output Unit: An output unit of a computer that provides the
information and results to outside world. Information from the CPU is
converted into an understandable form through output devices. The
output of the computer can be presented into different ways such as
software (display from monitor) and hardcopy (printed from printer).
iv. Storage / Memory Unit(MU): Memory is the location where data
and program are stores either permanently or temporarily. It also
saves the data for the future use. There are many categories/ types of
memory such as cache memory, primary memory and secondary
memory.
Q. Define microprocessor. What are its function?
Ans: A microprocessor is an electronic component that is used by a computer
to do its work. It is a central processing unit on a single integrated circuit chip
containing millions of very small components including transistors, resistors,
and diodes that work together.
Microprocessors use three steps commonly called Fetch, Decode,
and Execute. In the Fetch step, an instruction is copied from the
computer memory into the microprocessor. In the Decode step, the
microprocessor figures out what operation the instruction is meant to
do. In the Execute step, this operation is performed.
Function of CPU or microprocessor are:
•Controlling all other parts of the machine and sending timing signals.
•Transferring data between memory and I/O devices
•Fetching data and instructions from memory
•Decoding instruction
•Performing arithmetical and logical operations
•Executing programs stored in memory
•Performing communication among the I/O devices etc.
Q. What is a Bus? Write its types with figure.
Ans: A bus is a communication path that interconnects different
computer components.
Basically bus can be divided into two different types:
a. Internal( system ) bus e.g. data, address, control.
b. External (Expansion) bus e.g. ISA bus, AGP bus, PCI bus, USB, SCSI.
Depending on the type of information carried, bus are of 3 types:
i. Address bus
ii. Data bus
iii. Control bus.
i. Address bus: Address bus is a unidirectional pathway that carries
addresses generated by the microprocessor(CPU) to the memory and
Input/output (I/O) elements of the computer.
ii. Data bus: Data bus is a bidirectional in nature. Data flows along the
data bus from the CPU to memory during write operation and data
moves from memory to microprocessor during read operation.
iii. Control bus: Control bus carries the timing and control signals
necessary to coordinate the activities of the entire system. Control
bus is a bidirectional pathway .
Industry Standard Architecture Accelerated Graphics Port(video
(plugin modem, sound card) card)

USB( mouse,
keyboard)
SCSI( peripheral devices- Apple, PCs ,Unix system)

Peripheral Component Interconnect

( modem card, network card, sound card)
Q. What do you mean by memory ? List different types of the
computer memory. Explain them.
Ans: Memory is the storage device of the computer that storage data
either permanently or temporarily.
The different types of the computer memory are as follows:
i. Primary memory: The primary memory of the computer is also
called the internal memory of the computer. It is fast and less
capacity memory of computer. The primary memories of the
computers are ROM, RAM, cache, register etc. These memory is
called by different names like internal storage, primary storage,
main memory, volatile memory or simply memory.
The types of primary memory are:
a. Register
b. Cache
c. RAM
d. ROM
e. Buffer.
a. Register: Registers are the primary memory of the computer
system. They are mainly used to store data during the time of
processing inside ALU. They are the fastest memory of computer.
They are the temporary memory of computer system whose
storage capacity is very small.
b. Cache memory: Cache memory is extremely fast memory that is
built into a CPU. Cache memory is used to improve access times
and to enhance the overall performance of the computer. It is
temporary memory that bridges main memory (RAM) and CPU.
There are three types of cache memory:
i. Internal cache or level 1 or L1
ii. External cache or level 2 or L2
iii. L3 cache
i. Internal cache: Internal cache is a small amount of SRAM that is
placed inside the CPU that is accessed directly. It runs at the same
speed as the processor and enhance the performance. It is also
called level 1 or L1 cache memory.
ii. External cache or level 2 or L2: External cache is separate or
external from the CPU. It is often socket on the motherboard. L2
cache memory is much layer than L1 cache memory. L1 generally
has 16-64 KB and L2 has 512 KB-1MB. Most modern PCs also
come with external cache memory, called Level 2 (L2) caches.
These caches sit between the CPU and the DRAM.

iii. Level 3 or L3 cache: A memory bank built onto the motherboard or

within the CPU . The L3 cache feeds(supply) the L2 cache, and its
memory is typically slower than the L2 memory, but faster than
main memory.
c) RAM: RAM stands for Random Access Memory. The word “RAM” is
often associated with the volatile type of memory where the
information is lost after the power is switch off. This memory is
called by different name like internal memory, primary memory,
main memory .

Two Types of RAM:

i. SRAM(Static Random Access Memory).
ii. DRAM(Dynamic Random Access Memory)

The differences between SRAM and DRAM are as follows:

 SRAM DRAM
i. It stands for Static Random i. It stands for Dynamic
Access Memory. Random Access Memory.
ii. It is formed by using ii. It is formed by using
transistors. capacitors.
iii. It is very expensive. iii. It is cheaper than SRAM.
iv. It is faster than DRAM. iv. It is slower than SRAM.
v. It is mainly used as cache v. It is mainly used as main
memory. memory.
vi. It consume less electricity. vi. It consumes more
electricity.
d) ROM: ROM stands for Read Only Memory. The ROM is a non-
volatile memory because the contents of ROM are not lost even
after switching off the computer. ROM is a semiconductor static
chip program at the time of its manufacture and is not re-
programmable by the user. The program stored in ROM are called
firmware.

The types of ROM are:

i. PROM
ii. EPROM
iii. EEPROM
In summary,
i. PROM: PROM stands for Programmable Read Only Memory.
PROM is a blank ROM chip on which the manufacture can write
his own program, instruction and data only once. However, once
the program or data is written into ROM chip, it cannot be
changed. It is also known as OTP(One Time Programmable).

ii. EPROM: EPROM stands for Erasable Programmable Read Only

Memory. Once the PROM is programmed, it contents cannot be
changed. However, there is another types of memory chip called
EPROM that overcomes this problems. This memory chips are
used to stored programs that needs updating.
iii. EEPROM: EEPROM stands for Electrically Erasable Programmable
Read Only Memory. It is a special types of ROM that can be
erased by exposing it to a high voltage (21 volts) of an electrical
charged on byte. It is a type of non-volatile memory used in
computers and other electronic devices to store relatively small
amounts of data but allowing individual bytes to be erased and
reprogrammed.
e) Buffer: Buffer is a region of a physical memory storage used to
temporarily store data while it is being moved from one place to
another. Typically, the data is stored in a buffer as it is retrieved
from an input device (such as a microphone) or just before it is
sent to an output device (such as speakers). The buffer is also
used in online multimedia contents while playing the music and
video from the internet.
Memory Hierarchy in a computer system
ii) Secondary memory: Secondary memory is where programs and
data are kept on a long-term basis or permanently. Common
secondary storage devices are the hard disk and optical disks. It is
also known as auxiliary storage or external memory, is a
non-volatile memory.
a) Magnetic Tape: A magnetic tape is a sequential storage device of
computer. It is not common storage device nowadays. It is mainly
used in mainframe computers and super computers. It is slow
and sequential flow of data. It is very useful for storing huge
volume of data. It is cheaper and can be reused.

b) Flash memory: Flash memory is non-volatile data storage and

thus is capable of retaining its data even when its power has been
turned off. It is small, fast, light weighted and makes no noise. It is
reliable and allows you to specify which data you want to keep.
c) Pen drive: Pen drive is a portable USB (Universal Serial Bus). Flash
memory device that can be used to transfer audio, video and data
files from one computer to another computer. It is just like
external hard disk. USB flash drives are called thumb drive.
Storage capacity of pen drive is MB to GB.

d) Memory card: A memory card sometimes called a flash memory

card or a storage is a small storage medium used to store data
such as text, picture , audio, and video. It is a non-volatile
memory which means the data is stable on the memory card
when its power has between turned off.
e. Floppy Disk:
Alternatively referred to as a floppy or floppy disk, a floppy diskette is a type
of storage media capable of storing electronic data, like a computer file. The
floppy diskette was first created in 1967 by IBM as an alternative to buying
hard drives, which were extremely expensive at the time.
The picture shown on this page is an example of a 3.5" floppy diskette, one
of the most commonly used floppy diskettes, capable of storing 1.44 MB of
data.
f. Hard Disk:
A hard disk drive (sometimes abbreviated as a hard drive, HD, or HDD) is a
non-volatile data storage device. It is usually installed internally in a computer,
attached directly to the disk controller of the computer's motherboard. It
contains one or more platters, housed inside of an air-sealed casing. Data is
written to the platters using a magnetic head, which moves rapidly over them
as they spin.
Data stored on a computer's hard drive include the operating system,
installed software, and the user's personal files.
Spindle
Platter

Read/write head

HDD case
g. Zip Disk:
A Zip drive and Zip disk is a hardware data storage device developed by
Iomega that functions like a standard 1.44" floppy drive and diskette. What
makes the Iomega Zip drive unique is its capability to hold up to 100 MB of
data or 250 MB of data on the later models. Iomega Zip drives became very
popular in late 1990s but quickly became less popular as users needed larger
storage capabilities.

h. Memo stick:
The proprietary Sony Memory Stick was first
introduced by Sony in October 1998 and is a flash
memory card used with Sony digital cameras and
other Sony products. Sony released several models of
the Memory Stick, including the Memory Stick PRO,
Memory Stick Duo, Memory Stick PRO Duo, Memory
Stick Micro (M2), and Memory Stick PRO-HG. The
capacity of Memory Sticks range in size from 4 MB to
256 GB, with a theoretical maximum capacity of 2 TB.
i) Optical Disk: An optical disk is an electronic data storage medium
that can be written to and read using a low powered laser beam.
It is mainly used for music, movies and software programs. It is
compact, light weighted, durable. Optical disk are: CD-ROM, DVD-
ROM, CD-RW, CD-R etc.
i. CD ROM: CD ROM stands for
Compact Disk Read Only Memory.
CD ROM’s are popularly used to
distribute computer software
including games and multimedia
application.
 A large amount of data can be stored on a single disk. Once the
information is stored on the CD ROM, it becomes permanent
and cannot changed. The diameter of CD ROM is 12cm,thickness
is 1mm and weight about 18gm. The storage capacity of CD-
ROM is 250MB, 650MB, 700 MB to 1GB(1024MB).

ii. CD- RW: CD-RW stands for Compact Disk

Read /Write or Rewritable. The CD-RW is a new generation of
optical disk. It is erasable disk. The user can write and over write
data on the CD-RW disk many times. The CD-RW disc is also
known as erasable CD. However, the reliability of the disk tends
to decrease each time rewrite data.
iii) DVD-ROM/ DVD: DVD stands for Digital Versatile Dick or Digital
Video Disk. DVD is an extremely high capacity optical disk with
storage capacity from 4.7 GB to 17 GB. DVD disk is especially
used to store the movies or films, music, software ,etc. A DVD
looks like a CD ROM. DVD is a digital optical disk storage format
invented by Philips, Sony, Toshiba and Panasonic in 1995 A. D.

iv) Blu Ray Disc: Blu ray is also known as

Blue Ray Disc(BD). It was developed to enable
recording, rewriting and playback of High
Definition video(HD) as well as storing large amount of data. It
offers more than 5 times the storage capacity of traditional DVD
and can hold up to 25 GB on a single layer disk and 50 GB on a
dual layer disk.
Q. Differences between Primary and Secondary memory?
Ans: The differences between primary and secondary memory are:
Primary Secondary
i. It is directly connected to the i. It is not directly connected
processor. to the processor.

ii. It is categorized as volatile and ii. It is always non- volatile

non-volatile memories. memory.
iii. It has low storage capacity. iii. It has high storage
capacity.
iv. It is faster than secondary iv. It is slower than primary
memory. memory.
v. E.g. RAM, ROM, cache, register etc. v. Hard Drive, DVD, CD-
ROM, Pen drive etc.
Q. Differences between Magnetic disk and Optical disk?
Ans: The differences between Magnetic Disk and Optical Disk are:
Magnetic Disk Optical Disk
i. Data can be stored in form of i. Data can be stored in
circular tracks. form of spiral tracks.
ii. It has higher storage capacities. ii. It has lower storage
capacities.
iii. It can be damaged from water, iii. It cannot be damaged.
magnetic material etc.
iv. Data cannot be permanently iv. Data can be
burned on the disc. permanently burned on
the disc.
v. E.g magnetic tape, hard disk etc. v. E.g CD-ROM, DVD etc.
Q. Write short notes no smart card.
Ans: A smart card is a small card normally of the size of credit card or
ATM card or even smaller than that. We can store data or information
in the card. In order to read and write data on a smart card, a special
device called smart card reader is needed.

Q. What do you mean by peripheral device?

Ans: Computer peripheral are those devices
which are connected with computers.
Computers hardware are computer
Peripherals. E.g. keyboard, mouse, printer ,monitor etc.
Q. What is motherboard?
Ans: Motherboard is a PCB(Printed Circuit Board) of the computer
that consists of tiny chips and other electronic components. It is also
called system board. The motherboard serves to connect all of the
parts of a computer together. The CPU, memory, hard drives, and
other ports and expansion cards all connect to the motherboard
directly or via cables. Popular motherboard manufacturers include
ASUS, AOpen, Intel, ABIT, MSI, Gigabyte, and Biostar.
Input Devices:
Q. Define input devices.
Ans: The devices that are used to receive the data and instructions are
called input devices. These devices are used to input program and
data to the computer. These are the parts through which instructions
or data are given to a computer for processing purpose. These input
devices converts input data and instructions into a suitable binary
form which can be accepted by the computer.
Q. Write short notes on:
1. Keyboard: A computer keyboard is an input device used to enter
characters and functions into the computer system by pressing
buttons, or keys. It is the primary device used to enter text. A
keyboard typically contains keys for individual letters, numbers
and special characters, as well as keys for specific functions. A
keyboard is connected to a computer system using a cable or a
wireless connection. The individual keys for letters, numbers and
special characters are collectively called the character keys. The
most widely used layout in the English language is called QWERTY,
named after the sequence of the first six letters from the top left.
It was first invented, in 1868 A.D, in America by Christopher
Latham Sholes.
Types of keyboard:
a. XT keyboard (83 keys)
b. AT keyboard (101 keys)
c. Enhanced keyboard (more than 101 keys)
2. Pointing Device. A pointing device, or sometimes called a pointing
tool, is a hardware input device that allows the user to move the
mouse cursor in a computer program or GUI operating system. Using a
pointing device allows you to point at or manipulate any object or text
on the screen.
* Mouse: A mouse is a small input device which is used to point, draw
and select items that are displayed on the computer screen. The
pointer of the mouse is called a cursor. As we move the mouse across
the screen, the cursor moves according to the movement of the
mouse. It was invented in 1960 A.D by Douglas Englebart.
Types of mice are:
i. Ball Mouse/ mechanical mouse:
The ball mouse is one of the earliest forms of mice. It contained a ball
that could roll in all directions and track movement. The main
drawback of the ball mouse was that one had to constantly clean the
wheel of grime which would reduce the amount of friction.
ii. Optical Mouse:
Optical mice use LED(Light Emitting Diode) and photo technology to
detect movement, rather than a physically moving ball. Most optical
mice are plug and play, meaning you usually do not have to install any
software to make the mouse work. You simply plug it into its proper
connector, and your mouse is ready to be used.

iii. Laser Mouse:

Laser mice, as its name suggests, uses infrared laser technology to
detect the mouse’s movement. The laser mouse is very similar to
optical mice. Generally, laser mouse available nowadays is connected
to the USB (Universal Serial Bus) port. It is expensive than optical
mouse.
iv. Wireless mouse: A cordless mouse, also called a wireless mouse, is
a mouse that connects to a computer without the use of wires.
Instead, the mouse uses some manner of wireless technology, like
Bluetooth, or infrared radio waves. Usually, a USB receiver is plugged
into the computer and receives signals from the cordless mouse.
3. Joystick:
The joystick was invented, in 1944 A.D., in Germany but the video
game joystick was invented in, 1967 A.D. A joystick is a stick which is
mounted on a spherical ball which moves in a socket. It allows the
user to navigate easily around the display on the screen. A user may
move the stick on the device in different directions. This is
particularly useful at homes for playing video games and for
indicating positions in graphic systems.
4. Touch Pad:
A touch pad is a small touch-sensitive pad that is used as a pointing
device in portable computers i.e. laptop. It can be used in place of an
external mouse. It uses pressure sensors to track the position of a
device on its surface. Each position on the touch pad is translated to
the specific location on the screen. A touchpad is operated by using
your finger.
5. Track Ball:
A track ball is an upside down of a roller mouse. It was
used to be a basic input device in laptops earlier. It is
similar to the mouse. A trackball is a computer cursor
control device used in many notebook and laptop
computers. The trackball is usually located in front of the
keyboard toward the user.
6. Light Pen: A light pen is a light-sensitive pointing input
device commonly used to select or otherwise modify text
or data on a screen. Used with a CRT monitor, these
devices were an early form of manipulating and
highlighting data on the screen. Light pens were originally
developed around 1960s, they became more commonly
used with graphics cards. Today, light pens are no longer
used due to the invention of touch screens.
7. Touch Screen:
Touch screen is a kind of screen which is sensitive to user’s
touch. One can use a finger to point the command or
menu displayed on the screen. Touch screen was invented
in 2009 A.D, in Apple store. It is widely popular on laptops.
8. Microphone or Voice Input System:
A microphone nicknamed mic or mike is a device that
converts sound into an electrical signal. Microphones are used in
many applications such as telephones, public address systems for
concert halls and public events, live and recorded audio
engineering, sound recording, radios and television broadcasting
and in computers for recording voice, speech recognition, VoIP.
9. Scanner :
The scanner is an input device that needs images or text
and converts the data into digital signals. The image is
scanned and converted into a format that the PC can
interpret. It was invented by Rudolph Hell, in 1963 A.D, in
Germany. A scanner is a device that captures images from
photographic prints, posters, magazine pages, and similar
sources for computer editing and display. Scanners come
in hand-held, feed-in, and flatbed types and for scanning
black-and-white only, or color.
10. MIDI(Musical Instrument Digital Interface): Short
for Musical Instrument Digital Interface, MIDI is a
standard for digitally representing and transmitting sounds
that was first developed in the 1980s. The MIDI sound is
played back through the hardware device or computer.
Many older computer sound cards have a MIDI port.

MIDI

operated by a keyboard increase the volume of the sound

11. Digitizer( Graphic Tablet): A graphic tablet (also known
as a digitizer, drawing tablet, digital drawing tablet, pen
tablet, or digital art board) is a computer input device that
enables a user to hand-draw images, animations and
graphics, with a special pen-like stylus, similar to the way a
person draws images with a pencil and paper. These
tablets may also be used to capture data or handwritten
signatures.
12. Digital Camera: A digital camera is a hardware device
that takes pictures like a regular camera, but stores the
image as data instead of printing it to film. Many digital
cameras are capable of recording video in addition to
taking photos. The first digital camera was invented in
1975 by Steven Sasson, an engineer at Eastman Kodak. The
first digital cameras were used by the military and for
scientific purposes. Medical businesses and News
reporting companies began to use digital cameras a few
years later.
13. Bar Code Reader(BCR): A Bar Code Reader (BCR)
or scanner, also known as a Point of Sale (POS) scanner is
a hardware input device capable of reading a barcode. It
can also print out the details of the product or log
information about that product into a database. A perfect
example of a barcode reader is a supermarket barcode
scanner that reads and logs the price of a product. Today,
many smart phones with the proper apps are also capable
of scanning and reading barcodes. Lines of different widths
and sizes representing data.
14. OCR(Optical Character Reader):
Short for Optical Character Recognition or Optical
Character Reader, OCR is the process of taking
an image of letters or typed text and converting it
into digital data . A good example is companies and
libraries taking physical copies of books, magazines, or
other old printed material and using OCR to put them onto
computers. OCR is currently the best method of digitizing
typed pages of text.
15. MICR(Magnetic Ink Character Reader): MICR code 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 typically
includes the document-type indicator such as bank code,
bank account number, cheque number, cheque amount
etc.
16. OMR( Optical Mark Reader): Optical Mark reading
(OMR) is a method of entering data into a computer
system. Optical Mark Readers reads pencil or pen marks
made in pre-defined positions on paper forms. The OMR
technology could be used if data is to be collected from a
a large volume of data must be collected and processed in
a short period of time, information mainly include the
selection of categories or "tick box" answers to multiple-
choice questions.
Output Devices:
Q. Define output devices.
Ans: An output device is any device used to send data from a
computer to another device or user to display output. Most output
devices used by humans are in these categories. Examples monitors,
projectors, speakers, headphones and printers.
Types of output devices are:
i. Softcopy
ii. Hardcopy

i. Softcopy : A soft copy is an electronic copy of some type of data,

such as a file viewed on a computer's display or transmitted as an
e-mail attachment. E.g. monitor, speaker etc.

a. Monitor: A computer monitor, technically termed as a visual display

unit, can be plainly described as an electronic device that transmits
information from the computer onto a screen. Computer monitors are
available in a variety of shapes, designs, and colors. However, based
on the technology used to make computer monitors, they can be
broadly categorized into three types.
• CRT (Cathode Ray Tube)
• LCD (Liquid Crystal Display)
• LED (Light-Emitting Diodes)
• Touch screen
•CRT (Cathode Ray Tube): These monitors employ the CRT technology
used most commonly in the manufacturing of television screens.
These monitors are highly reliable and efficient, and are capable of
generating a resolution of up to 2048 x 1536 pixels(picture element).
CRT monitors are affordable and cost effective. These devices get
heated up very easily.

• LCD((Liquid Crystal Display):

Liquid crystal display, also known
as liquid crystal diode, is one of the most advanced technologies
available at present. Typically, an LCD monitor consists of a layer of
color or monochrome pixels. These monitors are compact, lightweight,
and do not consume much desk space. These monitors do not
consume much electricity and can even be operated by using
batteries.
• LED (Light-Emitting Diodes): LED monitors are the latest types of
monitors in the market today. LED monitors are said to use much
lesser power than CRT and LCD. They produce images with higher
contrast. Lifespan and durability of LED monitors is more than CRT or
LCD monitors.
• Touch screen: A touch screen is a display device that allows the user
to interact with a computer by using their finger. They can be quite
useful as an alternative to a mouse or keyboard for navigating a
graphical user interface (GUI). Touch screens are used on a variety of
devices such as computer and laptop monitors, smartphones, tablets
• Speaker: A computer speaker is a hardware softcopy output device
that connects to a computer to generate sound. The signal used to
produce the sound that comes from a computer speaker is created by
the computer's sound card.
ii. Hardcopy: A hard copy is a printed copy of information from a
computer. Sometimes referred to as a printout , a hard copy is so-
called because it exists as a physical object. E.g. printer, plotter.
• Printer: A printer is an external hardware output device that takes
the electronic data stored on a computer or other device and
generates a hard copy of it.
Types of printer are:
a) Impact printer e.g. dot-matrix printers, daisy-wheel printers, and
line printers etc.

b) Non- impact printer e.g. Laser, inkjet, Thermal printer etc.

 Impact printer / Dot-matrix Non impact Printer / Laser
Printer Printer
1. It prints characters or images 1. It prints characters and images
by striking print hammer or without striking the papers.
wheel against an inked ribbon.
2. Its speed is slower. 2. Its speed is faster.
3. Its printing quality is lower. 3. Its printing quality is higher.
4. It generates noise during 4. It does not generate noise
printing. during printing.
5. It uses inked ribbon for 5. It uses toner or cartridge for
printing. painting.
6. It is less expensive. 6. It is more expensive.
7. Dot matrix is an impact 7. Laser printer is a non-impact
printer. printer.
• Plotter: A plotter is a computer vector graphic printer that gives a
hard copy of the output based on instructions from the system.
Plotters are widely used to print designs of things such as cars, ships
and buildings on a piece of paper using a pen. They are also more
expensive than ordinary printers. A plotter is also known as a graph
plotter.
Q. Write short notes on:
• Dot-matrix printer
• Laser printer
• Inkjet printer.

Q. Differences between CRT and LCD monitor.

Ans: The differences between LCD and LED monitor are:
CRT LCD
i. It uses vacuum tube. i. It uses liquid crystal.
ii. It is harmful for eyes. ii. It is not harmful for the eyes.
iii. The picture quality is low. iii. The picture quality is high.
iv. It consumes high power. iv. It consumes low power.
v. It stands for Cathode Ray v. It stands for Liquid Crystal
Tube. Display.
Q. Define slot.
Ans: Expansion slots are easy to recognized on the motherboard. They
make up of a row of long plastic connector at the back of your
computer. It is used to communicate with the rest of the
computer devices. It is also known as expansion card, expansion
board, adapter card or accessory card.

Q. Define MODEM.
Ans: MODEM stands for modulator and Demodulator. A MODEM is a
device that enables a computer to transmit data over telephone
or cable lines. Computer information is stored digitally whereas
information transmitted over telephone lines is in the form of
analog signals.
 MODEM

Q. Define interface.
Ans: The term "interface" can refer to either a hardware connection or
a user interface. A hardware interface is used to connect two or
more electronic devices together. For example, a printer typically
connects to a computer via a USB interface.
Q. What is a port? Explain its types.
Ans: A port is a connection point that allows you to connect peripheral
devices like mouse, keyboard, speaker, printer etc.
The different types of port are:
i. Parallel port
ii. Serial port
iii. Fire-wire port(IEEE 1394)
iv. USB port (Universal Serial Bus)
v. PS/2

vi. Parallel port: Parallel port were originally developed by IBM as a

way to connect a printer to PC . It is also known as LPT(Line Print
Terminal) port. The standard parallel port is capable of sending
50-100 KB of data per second. They are unidirectional.
 Video Graphics Array (VGA) Serial Advanced Technology Attachment

Digital Visual Interface (DVI)

Registered Jack-45

HDMI (High-Definition Multimedia Interface)

Fire-wire port

LPT(Line Print Terminal)

communication
ii. Serial port: Serial port are called communication (COM) port which
supports sequential data transmission and are bidirectional.
Bidirectional communication allows each device to receive data as
well as transmit it. Data travels over serial port at 115KB per second.

iii. Firewire port: This port was originally created by Apple and
standardized in 1995 A.D. on the specification “IEEE 1394” (Institution
of Electricals and Electronic Engineering) high performance serial bus
and is very similar to USB port. It is easy to use , low implementation
cost and low cabling cost. Firewire is also available in wireless, CAT-5,
fiber optic and co-axial version.
CAT5 Firewire port

Fiber optic

wireless

coaxial
iv. USB port: In the past, connecting device to computer had been a
real headache. USB introduce in 1997 A.D. is a plug and play
peripheral connections which was invented to solve all these
headache. It is used to connect various devices such as scanner, digital
camera, speakers etc. to the computer.

v. PS/2 port: IBM developed PS/2 port. It is also called mouse port. It is
used to connect a computer mouse or keyboard. PS/2 connector is a
round connector with six pins. A color code is used to distinguish
between two ports, the keyboard port is purple and the mouse port
has green color.

keyboard mouse

Vi. HDMI( High Definition Multimedia Interface): High Definition

Multimedia Interface, HDMI is a connector and cable capable of
transmitting high-quality and high-bandwidth streams of audio and
video between devices. The HDMI technology is used with devices such
as an HDTV, Projector, DVD player. The HDMI standard was developed by
multiple companies, including Hitachi, Philips, Sony, and Toshiba.
vii. NIC card:
Network Interface Card, the NIC is also referred to as an
Ethernet card and network adapter. A NIC is a computer
expansion card for connecting to a network (e.g., home
network or Internet) using an Ethernet cable with an RJ-45
connector.

Due to the popularity and low cost of the Ethernet standard,

nearly all new computers have a network interface build
directly into the motherboard.
End of Unit 1