CHAPTER -1: COMPUTER ORGANISATION
1.1 Introduction to Computer
Computer is an electronic device that operates (works) under the control of programs
stored in its own memory unit.
A computer is an electronic machine that processes raw data to give information as
output.
An electronic device that accepts data as input, and transforms it under the influence
of a set of special instructions called Programs, to produce the desired output (referred
to as Information).
Explanations:
A computer is described as an electronic device because; it is made up of electronic
components and uses electric energy (such as electricity) to operate.
A computer has an internal memory, which stores data & instructions temporarily
awaiting processing, and even holds the intermediate result (information) before it is
communicated to the recipients through the Output devices.
It works on the data using the instructions issued, means that, the computer cannot do
any useful job on its own. It can only work as per the set of instructions issued.
A computer will accept data in one form and produce it in another form. The data is
normally held within the computer as it is being processed.
Program:
A computer Program is a set of related instructions written in the language of the
computer & is used to make the computer perform a specific task (or, to direct the
computer on what to do).
A set of related instructions which specify how the data is to be processed.
A set of instructions used to guide a computer through a process.
Data:
Data is a collection of raw facts, figures or instructions that do not have much meaning
to the user.
Data may be in form of numbers, alphabets/letters or symbols, and can be processed
to produce information.
Types of Data
There are two types/forms of data:
a). Digital (discrete) data:
Digital data is discrete in nature. It must be represented in form of numbers, alphabets or
symbols for it to be processed by a computer. Digital data is obtained by counting.
E.g. 1, 2, 3…
b). Analogue (continuous) data:
Analogue data is continuous in nature. It must be represented in physical nature in order to
be processed by the computer. • Analogue data is obtained by measurement. E.g. Pressure,
Temperature, Humidity, Lengths or currents, etc. The output is in form of smooth graphs from
which the data can be read.
Data Processing:
It is the process of collecting all items of data together & converting them into
information.
Processing refers to the way the data is manipulated (or handled) to turn it into
information.
The processing may involve calculation, comparison or any other logic to produce the
required result. The processing of the data usually results in some meaningful
information being produced.
Information:
Information is the data which has been refined, summarized & manipulated in the way
you want it, or into a more meaningful form for decision-making.
The information must be accurate, timely, complete and relevant.
1.2 Evolution of Computers
Computer evolution refers to the change in computer technology right from the time
computers were first used to the present. As computing evolves to higher system levels, so its
design also changes, from technical to socio-technical design.
The series of the evolution of computers are given below.
Abacus
Pascaline
Difference engine
Punched card equipment
ABC
UNIVAC – I
Abacus
The present day computers are a result of an evolutionary process which started way
back in 500 B.C. when Egyptian used a machine which is an early form of Abacus.
However the present form of Abacus is attributed to the Chinese and Japanese.
This is a machine, which was used for addition, subtraction, multiplication and division
operation.
Pascaline
In 1645 a device known as Pascaline was invented by French mathematician Blaise
Pascal.
The machine was also used per addition and subtraction purpose.
The device was operated by dialing a set of wheels.
In 1671 Leibniz improved on Pascal’s adding machine and invented the Leibniz’s
Calculator.
Difference engine
In 1822 Charles Babbage invented a Difference Engine.
The purpose of this device was to calculate the roots of polynomial equations and
prepare astronomy table for the British Navy.
He upgraded this to, invent an Analytical engine, which could store program
instructions initially coded on punched cards and subsequently shared internally.
Therefore Charles Babbage is known as the father of computers.
Punched card equipment
In 1890 Dr. H. Hollerith developed punched card equipment.
This equipment read the holes punched in the card and mechanically performed the
statistical analysis.
ABC (Atanasoff-Berry Computer )
The first pure electronic computer was invented by J. V. Atanasoff and C. Berry which
is known as Atanasoff-Berry Computer or ABC.
It used vacuum tubes for both data storage and data computation.
Subsequently Electronic Numerical Integrator and Calculator (ENIAC) was designed
and accepted as the general purpose computer.
UNIVAC
In 1945 John Von Neumann first gave the idea of sharing the same internal memory
for storing both data and instruction, which was subsequently adopted in every
computer organization.
On this principle subsequently Universal Automatic Computer (UNIVAC-1) was
invented
1.3 Generation of Computers
Computers are devices that accomplish tasks or calculations in accordance to a set of
directions, or programs. The first fully electronic computers, introduced in the 1940s, were
voluminous devices that required teams of people to handle. In comparison to those new
machines, today‘s computers are astounding. They are not only thousands of times more
expeditious, but also they can fit on your desk, on your lap, or even in your pocket.
Computers are such an integral part of our everyday life now most people take them for
granted.
Computers work through an interaction of hardware and software. The whole picture of
the computer goes back to decades. However there are five apparent generations of
computers. Each generation is defined by a paramount technological development that
changes necessarily how computers operate – leading to more compressed, inexpensive, but
more dynamic, efficient and booming machines.
First Generation – Vacuum Tubes (1940 – 1956)
These ancient computers utilized vacuum tubes as circuitry and magnetic drums for
recollection. As a result they were huge, actually taking up entire rooms and costing
resources to run. These were ineffective materials which produce a huge amount of heat,
sucked enormous electricity and subsequently engendered an abundance of heat which
caused perpetual breakdowns.
These first generation computers relied on ‗machine language‘ (which is the most
fundamental programming language that can be understood by computers). These
computers were limited to solving one problem at a time. Input was predicated on punched
cards and paper tape. Output emerged on print-outs. The two eminent machines of this era
were the UNIVAC and ENIAC machines – the UNIVAC is the first ever commercial computer
which was purchased in 1951 by a business named as the US Census Bureau.
Second Generation – Transistors (1956 – 1963)
The supersession of vacuum tubes by transistors, visualized the onset of the second
generation of computing. Although first invented in 1947, transistors weren‘t used
considerably in computers until the cessation of the 1950s. They were a huge development
over the vacuum tube, despite the fact still subjecting computers to destroying different levels
of heat. However they were extremely superior to the vacuum tubes, making computers
smaller, more expeditious, inexpensive and less burdensome on electricity use. They still
count on punched card for input/printouts.
The language emerged from strange binary language to symbolic (‗assembly‘) languages.
These meant programmers could discover instructions in words. Meanwhile during the same
time high caliber programming languages were being developed (early versions of COBOL
and FORTRAN). Transistor-driven machines were the first computers to store instructions
into their recollections, peregrinating from magnetic drum to magnetic core ‗technology‘. The
anticipatory versions of these machines were created for the atomic energy industry.
Third Generation – Integrated Circuits (1964 – 1971)
By this phase, transistors were now being miniaturized and put on silicon chips. This led to a
huge improvement in speed and effectiveness of these machines. These were the first
computers where users interacted utilizing keyboards and monitors who interfaced with an
operating system, a consequential leap up from the punch cards and printouts. This facilitated
these machines to run various applications at once utilizing a central program which functioned
to monitor memory.
As a result of these advances which again made machines more reasonable and more tiny,
a brand new group of users emerged during the ‗60s.
Fourth Generation – Microprocessors (1972 – 2010)
This innovation can be defined in one word: Intel. The chip-maker accomplished the Intel
4004 chip in 1971, which located all components of computer such as CPU, recollection,
input/output controls onto a single chip. What overcrowded a room in the 1940s now gets fit
in the palm of the hand. The Intel chip contained thousands of unified circuits. The year 1981
saw the first ever computer (IBM) categorically designed for home use and 1984 saw the
Macintosh introduced by Apple. Microprocessors even transformed beyond the realm of
computers and into an incrementing number of everyday products.
The incremented power of these small computers denoted they could be linked, establishing
networks. Which eventually led to the expansion, birth and rapid evolution of the Internet?
Other primary advances during this period have been the Graphical user interface (GUI), the
mouse and more of late the startling advances in laptop capability and hand-held
contrivances.
Fifth Generation – Artificial Intelligence (2010 Onwards)
Computer devices with artificial potentiality are still in development, but some of these
technologies are commencing to emerge and be used such as voice recognition. AI is an
authenticity, made possible by adopting parallel processing and superconductors. Inclining to
the future, computers will be thoroughly revolutionized again by quantum computation,
molecular and nano technology. The essence of fifth generation will be utilizing these
technologies to ultimately engender machines which can proceed and acknowledge natural
language, and have efficiency to determine and organize themselves.
Summary of Generation of computers
Features
1st
Generation
Computer
2nd Generation
Computer
3rd
Generation
Computer
4th Generation
Computer
Main
Switchin
g Device
Vacuum
Tube
Transistor
Integrat
ed
Circuit(I
C)
Large Scale
Integration(L
SI) & VLSI
Component
Size
6000
circuits/cubic
foot
10000
circuits/cubic
foot
10 millions
circuits/cu
bic foot
Over 500
billion
circuits/cubic
foot
Number of
instructions/se
c.
250
30,000
2,00,000
80 Millions
Meantime
between
failure
Hour
Days
Weeks
Months
Internal
memory
capacity
4000
characters
30000
characters
5,12,000
characters
Over 4
million
character
s
1.4 Classification of Computers
All the modern computers are broadly classified into the following three categories.
a) Analog Computer.
b) Digital Computer and
c) Hybrid Computer.
Analog computers
Are mostly used in industries in process control activities.
These computers work on analog data such as variation in temperature, pressure,
speed, voltage etc.
They are not general purpose computers; rather they are specific to a particular
application area. Therefore the cost of such computer varies from application to
application depending on the complexity.
The uses of such computers are very limited.
Digital computers
These computers are general purpose computers, which work on digital / binary data.
The speed and accuracy with which these computers work are very high.
Digital computers are also having several ranges from super computers to personal
computers.
Hybrid computers
Practically Hybrid computer are used to control the entire process.
The analog feature of such computer enables it to measure the physical quantities
such a temperature, pressure, voltage level etc. and convert them to digital data.
These data are then processed by the computer by using its digital data processing
capability.
The output from this computer may be taken in a paper as hardcopy, may be seen on
a display device or may be converted into analog form to automatically control various
processes.
Digital computers
Digital computers are classified into the following four categories:
o Super Computers.
o Mainframe Computers.
o Mini Computers.
o Micro Computer
Super computers
These computers are specifically designed to maximize the processing of floating point
instructions.
This is possible because of parallel processing technique which implements multiple
processors to work in parallel manner.
Such computers are very expensive and used in very high-end numerical processing,
geographical information system, etc.
Some of the popular super computers are Cray, Param, Anupam etc.
The speed of processing of super computers are measured in GFLOPS i.e., Giga
Floating Point Operations Per Second.
These computers used their own operating system and programming language and
hence vary from computer to computer.
Mainframe computers
These computers are intended for substantial high volume data processing.
These computers are characterized by–
• Large primary memory.
• Substantial processing capabilities. (MIPS)
• Substantial amount of peripheral devices that can be attached.
• A high data communication capability i.e. ability to connect thousands of terminals.
• Wide variety of memory size and terminal support option.
• Ability to handle large type computer application.
Application of Mainframe Computer
• space research,
• university connectivity,
• Wide area network (WAN) implementation etc.
Specification of mainframe computers.
• Processing speed – 30 to 100 million instruction per second (MIPS)
• Word length – More than 64 bits.
• I/O device –Wide range of peripheral devices.
• Internal Storage – More than 1 GB.
Mini Computers
• Fairly large primary memory.
• Medium scale processing capability i.e., lesser than mainframe but higher than
personal computers.
• Can connect up to 500 terminals on LAN.
• Supports wide range of application areas.
• Affordable, unlike mainframe computers by small business organization.
The application of mini computers
• The field of engineering and scientific organizations,
• Educational Institutes,
• Universities,
• Small/medium business organizations.
These computers are mainly used for medium or large volume data processing activity.
Specification of mini computer
• Processing speed – 10 to 30 MIPS.
• Word length – 32 bits.
• I/O device – Wide range of I/O devices can be connect.
• Internal storage – 66 MB to 512 MB.
Micro computers
This is the smallest and least expensive computers are or personal computers
popularly known as PC.
Typical features.
• These computers are portable.
• They require minimum power.
• Processing power is appropriate for handling most of the tasks.
• Memory capacity is sufficient to handle most of the tasks.
• Ease of use and support to various types of operating systems and application
softwares.
• Affordable price tag.
• These micro computers are further classified into three categories i.e., PC, PC-XT
and PC-AT.
Typical Specifications of PC
• Processor – I 8086 / I 8088 microprocessor.
• Memory – 640 KB of RAM
• Two 360 K Floppy Disk drive.
• Numerical Processor – I 8087.
• System bus –8 bit data bus & 16 bit address bus.
• Clock speed – 8 MHz
Personal Computer
• A PC-XT or Personal Computer with extended technology is an Up gradation of the
PC. It is having all the features discussed above. Apart from these the concept of
secondary memory / mass storage in the form of hard disk drive, was introduced for
the first time.
• The present days PC are PC-AT or personal computer with advanced technology.
Features of PC-AT
• Processor –I 80386 / 80486 / Pentium.
• Memory – 2 MB to 512 MB.
• Floppy disk drive 1.44 MB
• Hard disk drive 1.2 MB to 80 GB.
• System bus–32 bit to 64 bit.
• Clock speed–Up to 3 GHz
• Operating System –MS-DOS, Windows, UNIX, Linux etc.
1.5 Basic Organization of Computer (Functional Block diagram), Input
Devices, CPU & Output Devices.
A digital computer is considered to be a calculating device that can perform arithmetic
operations at enormous speed. It is defined as a device that operates upon information/data.
To be able to process data the computer is made of various functional units to perform its
specified task.
Block Diagram of Computer
Input Device:
Computers need to receive data and instruction in order to solve any problem.
Therefore, we need to input the data and instructions into the computers. The input unit
consists of one or more input devices. Keyboard is the one of the most commonly used input
device. Other commonly used input devices are the Mouse, Scanner, Microphone etc. All
the input devices perform the following functions.
• Accept the data and instructions from the outside world.
• Convert it to a form that the computer can understand.
• Supply the converted data to the computer system for further processing.
Central Processing Unit:
The Control Unit (CU) and Arithmetic Logic Unit (ALU) of the computer are together
known as the Central Processing Unit (CPU). The CPU is like brain performs the following
functions:
It performs all calculations.
It takes all decisions.
It controls all units of the computer.
Arithmetic Logical Unit:
All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It
also does comparison and takes decision. The ALU can perform basic operations
such as addition, subtraction, multiplication, division, etc and does logic operations
viz, >, <, =, ‗etc. Whenever calculations are required, the control unit transfers the
data from storage unit to ALU once the computations are done, the results are
transferred to the storage unit by the control unit and then it is send to the output unit
for displaying results.
Control Unit:
It controls all other units in the computer. The control unit instructs the input unit,
where to store the data after receiving it from the user. It controls the flow of data and
instructions from the storage unit to ALU. It also controls the flow of results from the
ALU to the storage unit.
The control unit is generally referred as the central nervous system of the computer
that control and synchronizes it‘s working.
Output Device:
The output unit of a computer provides the information and results of a computation to
outside world. Printers, Visual Display Unit (VDU) are the commonly used output
devices. Other commonly used output devices are Speaker, Headphone, and
Projector etc.
Storage Unit:
The storage unit of the computer holds data and instructions that are entered through
the input unit, before they are processed. It preserves the intermediate and final results
before these are sent to the output devices. It also saves the data for the later use. The
various storage devices of a computer system are divided into two categories.
a) Primary Storage: Stores and provides very fast. This memory is generally used to hold the
program being currently executed in the computer, the data being received from the input
unit, the intermediate and final results of the program. The primary memory is temporary in
nature. The data is lost, when the computer is switched off. In order to store the data
permanently, the data has to be transferred to the secondary memory. The cost of the
primary storage is more compared to the secondary storage. Therefore, most computers
shave limited primary storage capacity.
b) Secondary Storage: Secondary storage is used like an archive. It stores several
programs, documents, data bases etc. The programs that you run on the computer are first
transferred to the primary memory before it is actually run. Whenever the results are
saved, again they get stored in the secondary memory. The secondary memory is slower
and cheaper than the primary memory. Some of the commonly used secondary memory
devices are Hard disk, CD, etc.,
Memory Size:
All digital computers use the binary system, i.e. 0‘s and 1‘s. Each character or a
number is represented by an 8-bit code.
The set of 8 bits is called a byte. A character occupies 1-byte space. A numeric
occupies 2- byte space. Byte is the space occupied in the memory.
The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). One
KB is equal to 1024 bytes and one MB is equal to 1000KB. The size of the primary
storage in a typical PC usually starts at 16MB. PCs having 32 MB, 48MB, 128 MB,
256MB memory are quite common.
1.6 Computer Memory and Classification of Memory
Computer memory is a generic term for all of the different types of data storage
technology that a computer may use, including RAM, ROM, and flash memory.
Some types of computer memory are designed to be very fast, meaning that the
central processing unit (CPU) can access data stored there very quickly. Other types
are designed to be very low cost, so that large amounts of data can be stored there
economically.
Another way that computer memory can vary is that some types are non-volatile,
which means they can store data on a long term basis even when there is no power.
And some types are volatile, which are often faster, but which lose all the data stored
on them as soon as the power is switched off.
A computer system is built using a combination of these types of computer memory,
and the exact configuration can be optimized to produce the maximum data
processing speed or the minimum cost, or some compromise between the two.
Types of Computer Memory: Primary and Secondary
Although many types of memory in a computer exist, the most basic distinction is
between primary memory, often called system memory, and secondary memory,
which is more commonly called storage.
The key difference between primary and secondary memory is speed of access.
Primary memory includes ROM and RAM, and is located close to the CPU on the
computer motherboard, enabling the CPU to read data from primary memory very
quickly indeed. It is used to store data that the CPU needs imminently so that it does
not have to wait for it to be delivered.
Secondary memory by contrast, is usually physically located within a separate storage
device, such as a hard disk drive or solid state drive (SSD), which is connected to the
computer system either directly or over a network. The cost per gigabyte of secondary
memory is much lower, but the read and write speeds are significantly slower.
Over several periods of computer evolution, a wide of array of computer memory types
has been deployed, each with its own strengths and weaknesses.
Primary Memory Types: RAM and ROM
There are two key types of primary memory:
RAM, or random access memory
ROM, or read-only memory
Let’s look in-depth at both types of memory.
1) RAM Computer Memory
The acronym RAM stems from the fact that data stored in random access memory can be
accessed– as the name suggests – in any random order. Or, put another way, any random bit
of data can be accessed just as quickly as any other bit.
The most important things to understand about RAM are that RAM memory is very fast,
it can be written to as well as read, it is volatile (so all data stored in RAM memory is lost
when it loses power) and, finally, it is very expensive compared to all types of secondary
memory in terms of cost per gigabyte. It is because of the relative high cost of RAM
compared to secondary memory types that most computer systems use both primary and
secondary memory.
Data that is required for imminent processing is moved to RAM where it can be
accessed and modified very quickly, so that the CPU is not kept waiting. When the data is no
longer required it is shunted out to slower but cheaper secondary memory, and the RAM
space that has been freed up is filled with the next chunk of data that is about to be used.
Types of RAM
DRAM: DRAM stands for Dynamic RAM, and it is the most common type of RAM used in
computers. The oldest type is known as single data rate (SDR) DRAM, but newer computers
use faster dual data rate (DDR) DRAM. DDR comes in several versions including DDR2 ,
DDR3, and DDR4, which offer better performance and are more energy efficient than DDR.
However different versions are incompatible, so it is not possible to mix DDR2 with DDR3
DRAM in a computer system. DRAM consists of a transistor and a capacitor in each cell.
SRAM: SRAM stands for Static RAM, and it is a particular type of RAM which is faster than
DRAM, but more expensive and bulker, having six transistors in each cell. For those reasons
SRAM is generally only used as a data cache within a CPU itself or as RAM in very high-end
server systems. A small SRAM cache of the most imminently-needed data can result in
significant speed improvements in a system
The key differences between DRAM and SRAM are that SRAM is faster than DRAM –
perhaps two to three times faster – but more expensive and bulkier. SRAM is usually available
in megabytes, while DRAM is purchased in gigabytes.
DRAM uses more energy than SRAM because it constantly needs to be refreshed to
maintain data integrity, while SRAM – though volatile – does not need constant refreshing
when it is powered up.
2) ROM Computer Memory
ROM stands for read-only memory, and the name stems from the fact that while data can be
read from this type of computer memory, data cannot normally be written to it. It is a very fast
type of computer memory which is usually installed close to the CPU on the motherboard.
ROM is a type of non-volatile memory, which means that the data stored in ROM persists in
the memory even when it receives no power – for example when the computer is turned off. In
that sense it is similar to secondary memory, which is used for long term storage.
When a computer is turned on, the CPU can begin reading information stored in ROM
without the need for drivers or other complex software to help it communicate. The ROM
usually contains “bootstrap code” which is the basic set of instructions a computer needs to
carry out to become aware of the operating system stored in secondary memory, and to load
parts of the operating system into primary memory so that it can start up and become ready to
use.
ROM is also used in simpler electronic devices to store firmware which runs as soon as the
device is switched on.
Types of ROM
ROM is available in several different types, including PROM, EPROM, and EEPROM.
PROM: PROM stands for Programmable Read-Only Memory, and it is different from true ROM
in that while a ROM is programmed (i.e. has data written to it) during the manufacturing
process, a PROM is manufactured in an empty state and then programmed later using a
PROM programmer or burner.
EPROM: EPROM stands for Erasable Programmable Read-Only Memory, and as the name
suggests, data stored in an EPROM can be erased and the EPROM reprogrammed. Erasing
an EPROM involves removing it from the computer and exposing it to ultraviolet light before reburning
it.
EEPROM: EEPROM stands for Electrically Erasable Programmable Read-Only Memory, and
the distinction between EPROM and EEPROM is that the latter can be erased and written to
by the computer system it is installed in. In that sense EEPROM is not strictly read-only.
However in many cases the write process is slow, so it is normally only done to update
program code such as firmware or BIOS code on an occasional basis.
Secondary Memory
We know that processor memory, also known as primary memory, is expensive as well as
limited. The faster primary memory is also volatile. If we need to store large amount of data or
programs permanently, we need a cheaper and permanent memory. Such memory is called
secondary memory. Here we will discuss secondary memory devices that can be used to
store large amount of data, audio, video and multimedia files.
Characteristics of Secondary Memory
These are some characteristics of secondary memory, which distinguish it from primary
memory
It is non-volatile, i.e. it retains data when power is switched off
It is large capacities to the tune of terabytes
It is cheaper as compared to primary memory
Depending on whether secondary memory device is part of CPU or not, there are two types
of secondary memory – fixed and removable.
Let us look at some of the secondary memory devices available.
Hard Disk Drive
Hard disk drive is made up of a series of circular disks called platters arranged one over the
other almost ½ inches apart around a spindle. Disks are made of non-magnetic material like
aluminum alloy and coated with 10-20 nm of magnetic material.
Standard diameter of these disks is 14 inches and they rotate with speeds varying from 4200
rpm (rotations per minute) for personal computers to 15000 rpm for servers. Data is stored by
magnetizing or demagnetizing the magnetic coating. A magnetic reader arm is used to read
data from and write data to the disks. A typical modern HDD has capacity in terabytes (TB).
CD Drive
CD stands for Compact Disk. CDs are circular disks that use optical rays, usually lasers, to
read and write data. They are very cheap as you can get 700 MB of storage space for less
than a dollar. CDs are inserted in CD drives built into CPU cabinet. They are portable as you
can eject the drive, remove the CD and carry it with you. There are three types of CDs −
CD-ROM (Compact Disk – Read Only Memory) − The data on these CDs are
recorded by
the manufacturer. Proprietary Software, audio or video are released on CD-ROMs.
CD-R (Compact Disk – Recordable) − Data can be written by the user once on the
CD-R. It cannot be deleted or modified later.
CD-RW (Compact Disk – Rewritable) − Data can be written and deleted on these
optical disks again and again.
DVD Drive
DVD stands for Digital Video Display. DVD are optical devices that can store 15 times the data
held by CDs. They are usually used to store rich multimedia files that need high storage
capacity. DVDs also come in three varieties – read only, recordable and rewritable.
Pen Drive
Pen drive is a portable memory device that uses solid state memory rather than magnetic
fields or lasers to record data. It uses a technology similar to RAM, except that it is
nonvolatile. It is also called USB drive, key drive or flash memory.
Blu Ray Disk
Blu Ray Disk (BD) is an optical storage media used to store high definition (HD) video and
other multimedia filed. BD uses shorter wavelength laser as compared to CD/DVD. This
enables writing arm to focus more tightly on the disk and hence pack in more data. BDs can
store up to 128 GB data.
Solved Questions
Short Answer Type Questions.
Q.1 Outline the key features of 1st Generation Computer in brief.(2019-Winter)
Ans. The period of first generation was from 1946-1959. The computers of first
generation used vacuum tubes as the basic components for memory and circuitry
for CPU (Central Processing Unit). These tubes, like electric bulbs, produced a lot
of heat and the installations used to fuse frequently. Therefore, they were very
expensive and only large organizations were able to afford it. In this generation,
mainly batch processing operating system was used. Punch cards, paper tape,
and magnetic tape was used as input and output devices. The computers in this
generation used machine code as the programming language.
Q.2 What is CPU?(2018-Summer)
Ans. A central processing unit (CPU), also called a central processor, main processor
or just processor, is the electronic circuitry within a computer that executes
instructions that make up a computer program. The CPU performs basic
arithmetic, logic, controlling, and input/output (I/O) operations specified by the
instructions in the program.
Q.3 What is ALU?(2014-Winter)
Ans. Stands for “Arithmetic Logic Unit.” An ALU is an integrated circuit within a CPU or
GPU that performs arithmetic and logic operations. Arithmetic instructions include
addition, subtraction, and shifting operations, while logic instructions include
boolean comparisons, such as AND, OR, XOR, and NOT operations.
Q.4 Name three input devices used in PC.(2016-Summer)
Ans. The three input devices used in PC are Keyboard, Mouse and Scanner.
Long Answer Type Questions.
Q.1 Discuss about the generation of computers? Explain the key features of computers of
each generation?(2013-Winter)
Ans. A computer is an electronic device that manipulates information or data. It has the
ability to store, retrieve, and process data.
Nowadays, a computer can be used to type documents, send email, play games,
and browse the Web. It can also be used to edit or create spreadsheets,
presentations, and even videos. But the evolution of this complex system started
around 1940 with the first Generation of Computer and evolving ever since.
There are five generations of computers.
FIRST GENERATION
Features:
1946-1959 is the period of first generation computer.
J.P.Eckert and J.W.Mauchy invented the first successful electronic computer
called ENIAC, ENIAC stands for ―Electronic Numeric Integrated and Calculator‖.
Few Examples are: ENIAC, EDVAC, UNIVAC, etc.
Advantages:
It made use of vacuum tubes which are the only electronic component available
during those days.
These computers could calculate in milliseconds.
Disadvantages:
These were very big in size, weight was about 30 tones.
These computers were based on vacuum tubes.
These computers were very costly.
SECOND GENERATION
Features:
1959-1965 is the period of second-generation computer.
Second generation computers were based on Transistor instead of vacuum tubes.
Few Examples are: Honeywell 400, IBM 7094, etc.
Advantages:
Due to the presence of transistors instead of vacuum tubes, the size of electron
component decreased. This resulted in reducing the size of a computer as
compared to first generation computers.
Less energy and not produce as much heat as the first generation.
Assembly language and punch cards were used for input.
Disadvantages:
A cooling system was required.
Constant maintenance was required.
Only used for specific purposes.
THIRD GENERATION
Features:
1965-1971 is the period of third generation computer.
These computers were based on Integrated circuits.
IC was invented by Robert Noyce and Jack Kilby In 1958-1959.
IC was a single component containing number of transistors.
Few Examples are: PDP-8, PDP-11, ICL 2900, etc.
Advantages:
These computers were cheaper as compared to second-generation computers.
They were fast and reliable.
Use of IC in the computer provides the small size of the computer.
Disadvantages:
IC chips are difficult to maintain.
The highly sophisticated technology required for the manufacturing of IC chips.
Air conditioning is required.
FOURTH GENERATION
Features:
1971-1980 is the period of fourth generation computer.
This technology is based on Microprocessor.
A microprocessor is used in a computer for any logical and arithmetic function to
be performed in any program.
Graphics User Interface (GUI) technology was exploited to offer more comfort to
users.
Few Examples are: IBM 4341, DEC 10, STAR 1000, etc.
Advantages:
Fastest in computation and size get reduced as compared to the previous
generation of computer.
Heat generated is negligible.
Small in size as compared to previous generation computers.
Disadvantages:
The Microprocessor design and fabrication are very complex.
Air conditioning is required in many cases due to the presence of ICs.
Advance technology is required to make the ICs.
FIFTH GENERATION
Features:
The period of the fifth generation in 1980-onwards.
This generation is based on artificial intelligence.
The aim of the fifth generation is to make a device which could respond to natural
language input and are capable of learning and self-organization.
This generation is based on ULSI (Ultra Large Scale Integration) technology
resulting in the production of microprocessor chips having ten million electronic
components.
Few Examples are: Desktop, Laptop, etc.
Advantages:
It is more reliable and works faster.
It is available in different sizes and unique features.
It provides computers with more user-friendly interfaces with multimedia features. Disadvantages:
They need very low-level languages.
They may make the human brains dull and doomed.
Q.2 Discuss about the various input devices used in PC platform?(2013-Summer)
Ans. Following are some of the important input devices which are used in a
computer −
Keyboard
Keyboard is the most common and very popular input device which helps to input data
to the computer. The layout of the keyboard is like that of traditional typewriter, although
there are some additional keys provided for performing additional functions.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys
or 108 keys are also available for Windows and Internet.
Mouse
Mouse is the most popular pointing device. It is a very famous cursor-control device
having a small palm size box with a round ball at its base, which senses the movement of
the mouse and sends corresponding signals to the CPU when the mouse buttons are
pressed.
Generally, it has two buttons called the left and the right button and a wheel is present
between the buttons. A mouse can be used to control the position of the cursor on the
screen, but it cannot be used to enter text into the computer.
Joystick
Joystick is also a pointing device, which is used to move the cursor position on a
monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The
lower spherical ball moves in a socket. The joystick can be moved in all four directions.
Joystick
The function of the joystick is similar to that of a mouse. It is mainly used in Computer
Aided Designing (CAD) and playing computer games.
Light Pen
Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or
draw pictures on the monitor screen. It consists of a photocell and an optical system
placed in a small tube.
When the tip of a light pen is moved over the monitor screen and the pen button is
pressed, its photocell sensing element detects the screen location and sends the
corresponding signal to the CPU.
Track Ball
Track ball is an input device that is mostly used in notebook or laptop computer, instead
of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the
pointer can be moved.
Since the whole device is not moved, a track ball requires less space than a mouse. A
track ball comes in various shapes like a ball, a button, or a square.
Scanner
Scanner is an input device, which works more like a photocopy machine. It is used when
some information is available on paper and it is to be transferred to the hard disk of the
computer for further manipulation.
Scanner captures images from the source which are then converted into a digital form
that can be stored on the disk. These images can be edited before they are printed.
Digitizer
Digitizer is an input device which converts analog information into digital form. Digitizer
can convert a signal from the television or camera into a series of numbers that could be
stored in a computer. They can be used by the computer to create a picture of whatever
the camera had been pointed at.
Digitizer is also known as Tablet or Graphics Tablet as it converts graphics and pictorial
data into binary inputs. A graphic tablet as digitizer is used for fine works of drawing and
image manipulation applications.
Microphone
Microphone is an input device to input sound that is then stored in a digital form.
The microphone is used for various applications such as adding sound to a multimedia
presentation or for mixing music.
Magnetic Ink Card Reader (MICR)
MICR input device is generally used in banks as there are large number of cheques to be
processed every day. The bank’s code number and cheque number are printed on the
cheques with a special type of ink that contains particles of magnetic material that are
machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main
advantages of MICR is that it is fast and less error prone.
Optical Character Reader (OCR)
OCR is an input device used to read a printed text.
OCR scans the text optically, character by character, converts them into a machine
readable code, and stores the text on the system memory.
Bar Code Readers
Bar Code Reader is a device used for reading bar coded data (data in the form of light
and dark lines). Bar coded data is generally used in labelling goods, numbering the
books, etc. It may be a handheld scanner or may be embedded in a stationary scanner.
Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which
is then fed to the computer that the bar code reader is connected to.
Optical Mark Reader (OMR)
OMR is a special type of optical scanner used to recognize the type of mark made by pen
or pencil. It is used where one out of a few alternatives is to be selected and marked.
It is specially used for checking the answer sheets of examinations having multiple
choice questions.
Course Duration :- 12 Months
Class Daily: Mon to Sat
Daily : 1 Hrs Class
Course Fee : Rs. 12500
Class Open Time : 8:00 AM
Class Close Time : 8:00 PM