The document summarizes the five generations of computers from the first generation in 1946-1959 based on vacuum tubes to the current fifth generation from 1980 onwards based on artificial intelligence. Each generation is defined by the underlying technology used in processors. The first generation used vacuum tubes, second used transistors, third used integrated circuits, fourth used microprocessors, and fifth uses ULSI microprocessors. Each generation provided improvements in size, speed, reliability and capabilities over previous generations. The document also provides examples of computers from each generation and discusses their characteristics.

1. Generations of Computer
Introduction:
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
Introduction:
 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
 IBM-701
 IBM-650
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.
 It could store only a small amount of information due to the presence of magnetic
drums.

2. As the invention of first generation computers involves vacuum tubes, so another
disadvantage of these computers was, vacuum tubes require a large cooling system.
 Very less work efficiency.
 Limited programming capabilities and punch cards were used to take inputs.
 Large amount of energy consumption.
 Not reliable and constant maintenance is required.
SECOND GENERATION
Introduction:
 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
 CDC 1604
 CDC 3600
 UNIVAC 1108
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 genration.
 Assembly language and punch cards were used for input.
 Low cost than first generation computers.
 Better speed, calculate data in microseconds.
 Better portability as compared to first generation
Disadvantages:
 A cooling system was required.
 Constant maintenance was required.
 Only used for specific purposes.
THIRD GENERATION
Introduction:

3.  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
 IBM 360
 IBM 370
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.
 IC not only reduce the size of the computer but it also improves the performance of
the computer as compared to previous computers.
 This generation of computers has big storage capacity.
 Instead of punch cards, mouse and keyboard are used for input.
 They used an operating system for better resource management and used the concept
of time-sharing and multiple programming.
 These computers reduce the computational time from microseconds to nanoseconds.
Disadvantages:
 IC chips are difficult to maintain.
 The highly sophisticated technology required for the manufacturing of IC chips.
 Air conditioning is required.
FOURTH GENERATION
Introduction:
 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.

4.  Graphics User Interface (GUI) technology was exploited to offer more comfort to
users.
Few Examples are:
 IBM 4341
 DEC 10
 STAR 1000
 PUP 11
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.
 Less maintenance is required.
 All types of high-level language can be used in this type of 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
Introduction:
 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 component.
Few Examples are:
 Desktop
 Laptop
 NoteBook
 UltraBook
 Chromebook
Advantages:
 It is more reliable and works faster.

5.  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.
S.No Generation & Description
1
First Generation
The period of first generation: 1946-1959. Vacuum tube based.
2
Second Generation
The period of second generation: 1959-1965. Transistor based.
3
Third Generation
The period of third generation: 1965-1971. Integrated Circuit based.
4
Fourth Generation
The period of fourth generation: 1971-1980. VLSI microprocessor based.
5
Fifth Generation
The period of fifth generation: 1980-onwards. ULSI microprocessor based.
Basic Organization of a Computer:
The main component of basic organization of a computer system is micro-
processor(C.P.U), memory unit(MU), and input-output devices.
Explanation: CPU : CPU is a brain of computer. It controls the computer system

6. Input Unit:
o It accepts (or reads) instructions and data from outside.
o It converts these instructions and data in computer acceptable form
o It supplies the converted instructions and data to the computer system for
further processing.
Central Processing Unit (CPU):
Control Unit:
Control unit of a computer system manages and coordinates the operations of
all other components of the computer system.
Arithmetic Logic Unit(ALU):
Arithmetic logic unit of a computer system is the place, where the actual executions
of instruction, takes place during processing operation.
Storage Unit:
Primary Memory:
It is volatile ( loses data on power dissipation). It is used to hold running program
instruction, data, intermediate results, and results of on-going processing of jobs.

7. Secondary Memory:
It is non-volatile (retains data even without power).It is used to hold stored program
instructions and a large volume of information.
Output Unit:
o It accepts the results produced by the CPU.
o It converts these coded results to human acceptable form.
o It supplies the converted results to outside world.
Number System.
The technique to represent and work with numbers is called number system. Decimal
number system is the most common number system. Other popular number systems include
binary number system, octal number system, hexadecimal number system, etc.
A computer can understand the positional number system where there are only a few symbols
called digits and these symbols represent different values depending on the position they
occupy in the number.
 The value of each digit in a number can be determined using −
 The digit
 The position of the digit in the number
 The base of the number system
Decimal Number System
The number system that we use in our day-to-day life is the decimal number system.
Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number
system, the successive positions to the left of the decimal point represent units, tens,
hundreds, thousands, and so on.
Each position represents a specific power of the base (10). For example, the decimal number
1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds
position, and 1 in the thousands position. Its value can be written as

8. (1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l)
1 x 103
)+ (2 x 102
)+ (3 x 101
)+ (4 x l00
)
1000 + 200 + 30 + 4
1234
As a computer programmer or an IT professional, you should understand the following
number systems which are frequently used in computers.
S.No. Number System and Description
1 Binary Number System
Base 2. Digits used : 0, 1
2
Octal Number System
Base 8. Digits used : 0 to 7
3
Hexa Decimal Number System
Base 16. Digits used: 0 to 9, Letters used : A- F
Binary Number System
Characteristics of the binary number system are as follows −
 Uses two digits, 0 and 1
 Also called as base 2 number system
 Each position in a binary number represents a 0 power of the base (2). Example 20
 Last position in a binary number represents a x power of the base (2). Example
2x
where x represents the last position - 1.
Example
Binary Number: 101012
Calculating Decimal Equivalent −
Step Binary Number Decimal Number
Step 1 101012 ((1 x 24
) + (0 x 23
) + (1 x 22
) + (0 x 21
) + (1 x 20
))10
Step 2 101012 (16 + 0 + 4 + 0 + 1)10
Step 3 101012 2110

9. Note − 101012 is normally written as 10101.
Octal Number System
Characteristics of the octal number system are as follows −
 Uses eight digits, 0,1,2,3,4,5,6,7
 Also called as base 8 number system
 Each position in an octal number represents a 0 power of the base (8). Example 80
 Last position in an octal number represents a x power of the base (8). Example
8x
where x represents the last position - 1
Example
Octal Number: 125708
Calculating Decimal Equivalent −
Step Octal Number Decimal Number
Step 1 125708 ((1 x 84
) + (2 x 83
) + (5 x 82
) + (7 x 81
) + (0 x 80
))10
Step 2 125708 (4096 + 1024 + 320 + 56 + 0)10
Step 3 125708 549610
Note − 125708 is normally written as 12570.
Hexadecimal Number System
Characteristics of hexadecimal number system are as follows −
 Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
 Letters represent the numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E =
14, F = 15
 Also called as base 16 number system
 Each position in a hexadecimal number represents a 0 power of the base (16).
Example, 160
 Last position in a hexadecimal number represents a x power of the base (16).
Example 16x
where x represents the last position - 1
Example
Hexadecimal Number: 19FDE16
Calculating Decimal Equivalent −

10. Step Binary
Number
Decimal Number
Step 1 19FDE16 ((1 x 164
) + (9 x 163
) + (F x 162
) + (D x 161
) + (E x 160
))10
Step 2 19FDE16 ((1 x 164
) + (9 x 163
) + (15 x 162
) + (13 x 161
) + (14 x 160
))10
Step 3 19FDE16 (65536+ 36864 + 3840 + 208 + 14)10
Step 4 19FDE16 10646210
Binary Number System
The binary number system, also called the base-2 number system, is a method of
representing numbers that counts by using combinations of only two numerals: zero (0) and
one (1). Computers use the binary number system to manipulate and store all of their data
including numbers, words, videos, graphics, and music.

11. Here are some examples of converting binary directly into decimal. We simply add
up the place values of each 1 digit in the binary number.
 1001012 = 3710:
Exponents 25 24 23 22 21 2
0
Place Values 32 16 8 4 2 1
Bits 1 0 0 1 0 1
Value 32 + 4 + 1 = 37
 100011102 = 14210:
Exponents 27 26 25 24 23 22 21 2
0
Place Values 128 64 32 16 8 4 2 1
Bits 1 0 0 0 1 1 1 0
Value 128 + 8 + 4 + 2 = 142
 1111010002 = 48810:
Exponents 28 27 26 25 24 23 22 21 2
0
Place Values 256 128 64 32 16 8 4 2 1
Bits 1 1 1 1 0 1 0 0 0
Value 256 + 128 + 64 + 32 + 8 = 488
 101101012 = 18110:
Exponents 27 26 25 24 23 22 21 2
0
Place Values 128 64 32 16 8 4 2 1
Bits 1 0 1 1 0 1 0 1
Value 128 + 32 + 16 + 4 + 1 = 181
PLANNING THE COMPUTER PROGRAM
The Programming Process - Purpose
Understand the problem
Read the problem statement
Question users
Inputs required
Outputs required
Special formulas
Talk to users

12. Plan the logic
Visual Design Tools
Input record chart
Printer spacing chart
Hierarchy Chart
Flowchart
Verbal Design Tools
Narrative Description
Pseudocode
Code the program
Select an appropriate programming language
Convert flowchart and/or Pseudocode instructions into programming language statements
Test the program
Syntax errors
Runtime errors
Logic errors
Test Data Set
Implement the program
Buy hardware
Publish software
Train users
Implementation Styles
Crash
Pilot
Phased
Dual
Maintain the program
Maintenance programmers
Legacy systems
Up to 85% of IT department budget
Problem solving with computers involves several steps:
1. Clearly define the problem.
2. Analyze the problem and formulate a method to solve it (see also “validation”).
3. Describe the solution in the form of an algorithm.
4. Draw a flowchart of the algorithm.
5. Write the computer program.
6. Compile and run the program (debugging).
7. Test the program (debugging) (see also “verification”).

13. 8. Interpretation of results.
Verification and Validation
If the program has an important application, for example to calculate student grades or guide a rocket,
then it is important to test the program to make sure it does what the programmer intends it to do and
that it is actually a valid solution to the problem. The tests are commonly divided as follows:
Verification
Verification verify that program does what you intended it to do; steps 7(8) above attempt
to do this.
Validation does the program actual solve the original problem i.e. is it valid? This goes
back to steps 1 and 2 - if you get these steps wrong then your program is not a
valid solution.