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Introduction to Computers
and Computer Generation

Basics of Computer & ‘C’ programming

(CMP 104)

What Is Computing?
Computing is an activity that needs
◦ computers to perform a task, or
◦ create Computers.

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Tasks
• Designing and building hardware systems.
• Designing and building software systems.
• Processing, structuring, and managing
information;
• Doing scientific research using computers;
• Creating Intelligent systems;
• Creating and using communications media;
• Creating and using entertainment media;
The list is endless, and the possibilities are vast.

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Computer Definition

A computer is an electronic device, operating
under the control of instructions (software)
stored in its own memory unit, that can
accept data (input), manipulate data (process),
and produce information (output) from the
processing.
Generally, the term is used to describe a
collection of devices that function together as
a system.

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Block Diagram along with
Computer Component !

Input Processing Output

5

Components of Computer
The basic components of a computer are:
Input Unit
Output Unit
Memory / Storage Unit
Arithmetic Logic Unit
Control Unit
Central Processing Unit

6

W�� a computer is asked to do a job, it handles
the task in a very special way:
1)It accepts the information from the user. This is
called input.
2)It stores the information until it is ready for use.
The computer has memory chips, which are
designed to hold information until it is needed.
3)It processes the information. The computer has
an electronic brain called the Central Processing
Unit, which is responsible for processing all data
and instructions given to the computer.
4)It then returns the processed information to the
user. This is called output.
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Input Unit
Input Unit accepts the instructions and data
from the outside world.
Then it converts these instructions and data
in computer acceptable form.
After that it supplies the converted
instructions and data to the computer
system for further processing.

8

Memory Unit
The Memory Unit is the part of the computer
that holds data and instructions for processing.
Memory associated with the CPU is also called
primary storage, primary memory, main
storage, internal storage and main memory.
There are two types of memory inside the
computer:
1. Primary Memory
2. Secondary Memory

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MEMORY
Primary Memory-- Primary storage or
memory: Is where the data and program
that are currently in operation or being
accessed are stored during use.
Secondary Memory-- Stores instructions
and data between sessions
◦ A file stores data or instructions in
secondary memory

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Primary Memory
◦ Consists of electronic circuits: Extremely fast
and expensive.
◦ Two types:
 RAM (non-permanent)
 Programs and data can be stored here for the computer’s
use.
 Volatile: All information will be lost once the computer
shuts down.
 ROM (permanent)
 Contents do not change.

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Secondary Memory
A computer might have any of these
types of secondary memory
◦ Hard disk
 Fast
 Fixed in the computer and not normally removed
◦ Floppy disk
 Slow
 Easily shared with other computers
◦ Compact disk
 Slower than hard disks
 Easily shared with other computers
 Can be read only or re-writable

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Central Processing Unit(CPU)
The control unit(CU) and ALU of a
computer system are jointly known as the
CPU.
The CPU is the brain of computer system.
An arithmetic logic unit (ALU) is a digital
circuit that performs arithmetic and logical
operations.
The ALU is a fundamental building block of
the central processing unit (CPU) of a
computer. 13

Control Unit
The control unit (control system or central
controller) directs the various components
of a computer.
It reads and interprets (decodes)
instructions in the program one by one.
The control system decodes each
instruction and turns it into a series of
control signals that operate the other parts
of the computer.
14

Output Unit
The output unit is just reverse of the input
unit.
It accepts the result produced by computer,
which are in coded form and can't be easily
understood by us.
Then it converts these coded result into
human readable form.
After that it supplies the converted results
to the outside world.
15

Primary storage (memory)
Colum #
0 1 2 3
Row #
0

Data 1
2 ADDRESS
Segment 3
(Row #, Col 3)
4 (2,0)
(2,0)

5 (4,3)
(4,3)

Code 6 (3,2)

Segment 7
8
(9,2)
(9,2)

9

Data
C (2,0)+C(4,3) → C(3,2)

Code : Add content of address (2,0) and content of address (4, 3)
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and store the result at (3,2) i.e. replace the C(3,2) by C

Store the data item 50 at address
(2,0)
1. Ask the input device to take
the number 50 and send it to
the main memory.
2. Ask the control unit to store
it in the data segment at
memory cell address (2,0).

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Store the data item 60 at address
(4,3)
the number 60 and send it
to the main memory.
4. Ask the control unit to
store it in the data segment
at memory cell address
(4,3).
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Store the instruction C (2,0)+C(4,3)
→ C(3,2) at address (9,2)
the instruction C (2,0)+C(4,3)
→ C(3,2) and send it to the
main memory.
6. Ask the control unit to store it
in the code segment at main
memory cell address (9,2).
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Instruction execution
Ask the control unit to
ask the ALU to execute
the instruction given at
the cell address (9,2).

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ALU Executes C (2,0)+C(4,3) →
C(3,2)
• Takes 50 from the cell (2,0) and keeps it in
his blue cell
50
• Takes 60 from the cell (4,3) and keeps it in
his red cell
60
• Adds contents of blue and red cells and
keeps the result in green cell +
→ 50 60 110

• Asks control unit to send (store, copy, …)
the content of green cell into the data
segment cell at address (3,2)

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Step-by-Step Execution Process
Colum #
0 1 2 3
Row #
0

Data 1
2 ADDRESS
Segment 50 3
(Row #, Col 3)
110 (2,0)
(2,0)
60
4

5 (4,3)
(4,3)

Code 6 (3,2)

Segment 7
8
(9,2)
(9,2)

9

50 60 110
Code : Add the content of the address (2,0) and the content of the address
(4, 3) and store the result at (3,2) i.e. replace the C(3,2) by C (2,0)+C(4,3) .
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What characteristics computers
have?
• Automatic: It is automatic because a
computer works by itself without much
human intervention.
• Speed :As compared to human, a
computer works at a very high speed.
Speed is measured in millisecond (10-3) but
in microseconds (10-6), nanoseconds (10-9),
picoseconds (10-12). A computer can
perform several billions (109) operations
like +, -, / … per second.
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have?
Accuracy : Computers are very
accurate but accuracy depends on their
hardware and software design, and the
correctness of the input data. Remember!
Garbage in garbage out.
Diligence: Computers work diligently
meaning they perform their task , from
start to end, with uniform accuracy and
speed.
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have?
• Versatility: Computers are versatile
because they can perform different types
of tasks.
• Power of remembering: Computers
can store and recall (retrieve) a large
number of data and extract information
from them.
• No Feeling or emotions: Computers
do not have feeling or emotions yet.

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Computer Generations
 Each generation of Computer is characterized by a
major technological development that fundamentally
changed the way computers operate, resulting in
smaller, cheaper, more powerful and more efficient and
reliable devices.
The various generations of computers an listed
below
 First Generation(1946-1954)
 Second Generation(1955-1964)
 Third Generation(1965-1977)
 Fourth Generation(1978-1991)
 Fifth Generation(1992-continued)

First Generation(1946-1954)
 The digital computes using electronic valves (Vacuum
tubes) are known as first generation computers.
 They stored information in the form of propagating sound
waves.
 Some of the computers of this generation were:
1. Mark I ( IBM Automatic Sequence Controlled
Calculator (ASCC))
1. ENIAC: Electronic Numerical Integrator and
Calculator developed in 1946
2. EDVAC: It stands for Electronic Discrete Variable
Automatic Computer developed in 1950
3. EDSAC: It stands for Electronic Delay Storage
Automatic Computer developed in 1949.
4. UNIVAC-1: Universal Accounting Computer in 1951.

Limitations
1. They used valves or vacuum tubes as their main
electronic component.
2. They were large in size, slow in processing and
had less storage capacity.
3. They consumed lots of electricity and produced
lots of heat.
4. Their computing capabilities were limited.
5. They were not so accurate and reliable.
6. They used machine level language for
programming.
7. They were very expensive.

Second Generation (1955-1964)
 They used transistors for CPU components , ferrite cores
for main memory & magnetic disks for secondary
memory. They used high-level languages such as FORTRAN
(1956), ALGOL (1960) & COBOL (1960 – 1961).
 In this generation concept of Central Processing Unit
(CPU), memory, programming language and input and output
units were developed.
 Some of the computers of the Second Generation were
1. IBM 1620: Its size was smaller as compared to First
Generation computers and mostly used for scientific purpose.
2. IBM 1401: Its size was small to medium and used for business
applications.
3. CDC 3600: Its size was large and is used for scientific
purposes.

Features
1. Transistors were used instead of Vacuum
Tube.
2. Processing speed is faster than First
Generation Computers (Micro Second)
3. Smaller in Size.
4. The input and output devices were faster.
Example: IBM 1400 and 7000 Series, Control
Data 3600 etc.

Third Generation(1965-1977)
This generation made use of IC’s.
These ICs are popularly known as Chips and a small
chip consist of the capacity of the 300 transistors.
Higher level language such as BASIC (Beginners
All purpose Symbolic Instruction Code) was
developed during this period.
Some of the computers developed during this period
were IBM-360, ICL-1900, IBM-370, and VAX-
750.

Features
1. They used Integrated Circuit (IC) chips in
place of the transistors.
2. Semi conductor memory devices were used.
3. The size was greatly reduced, the speed of
processing was high, they were more
accurate and reliable.
4. The mini computers were introduced in this
generation.
5. They used high level language for
programming.

Fourth Generation(1978-1991)
 An IC containing about 100 components is called LSI (Large
Scale Integration) and the one, which has more than 1000
such components, is called as VLSI (Very Large Scale
Integration).
 It uses large scale Integrated Circuits (LSIC) built on a single
silicon chip called microprocessors.
 Due to the development of microprocessor it is possible to
place computer’s central processing unit (CPU) on single chip.
These computers are called microcomputers.
 Keyboards, dot matrix printers etc. were developed.
 OS-such as MS-DOS, UNIX, Apple’s Macintosh were
available.
 The personal computer (PC) is a Fourth Generation
Computer

Features
1.  They used Microprocessor (VLSI) as their main
switching element.
2. They are also called as micro computers or
personal computers.
3.  Their size varies from desktop to laptop or
palmtop.
4.  They have very high speed of processing; they
are 100% accurate, reliable,   diligent and
versatile.
5.  They have very large storage capacity.
Example: IBM PC, Apple-Macintosh etc.

Fifth Generation(1992-Continued)
It uses ULSI (Ultra-Large Scale Integration) chips.
Millions of transistors are placed in a single IC in ULSI
chips.
 64 bit microprocessors have been developed during
this period.
Memory chips and flash memory up to 1 GB, hard
disks up to 600 GB & optical disks up to 50 GB have
been developed.
Some technological developments that could make more
development of fifth generation computers possible,
include:-
Parallel Processing
Super Computers
Efficient Speech Recognition system

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