The Five Generations of Computers Explained with Stage by Stages

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The term ‘computer generation’ is often used in relation to the hardware of computers. Each phase of computer development is known as a separate generation of computers. Each phase of development is characterised by the type of switching circuits it utilized.Most computers today use the idea of ‘stored program computer’, proposed by Dr. John Von Neumann in 1945.

The architecture of a computer is based on three key concepts;
i. Data and instructions are stored in a single read-write memory.
ii. The memory contents are addressable by locations.
iii. Execution takesplace in a sequential fashion, from one instruction to the next unless modified  explicity.
First Generation Computers (1949-55)
The first generation used vaccum tubes, and machine laguage was used for giving instructions. They used the concept of ‘stored program’. They were very large in size and their programming was a difficult task. Some computers of first generation are,i. ENIAC: Electronic Numerical Integrator And Calculator (ENIAC) was the first electronic computer developed.It has a very small memory. Their programs are wired on boards. The addition of two numbers was achieved in 200 microseconds and multiplication in 2000 microseconds.
ii. EDVAC: The binary arithmetic was used in the construction of computer called the Electronic Discrete Variable Automatic Computer (EDVAC). The Von Neumann concept of stored program was also applied in EDVAC.
With this, the operations became faster since the computer could rapidly access both the program and data.
iii. EDSAC: The Electronic Delay Storage Automatic Computer (EDSAC) used mercury delayed lines for storage. It also used Neumann concept of stored program. This allowed easy implementation of programloops. The
addition operation was accomplished in 1500 microseconds and multiplication operation in 4000 micro  seconds.
iv. UNIVAC-I: The Universal Automatic Computer (UNIVAC) was the first digital computer developed. Initial applications of computers were in science and engineering but with the advent of UNIVAC-I, the commercial
applications started. The first generation computers suffered from some ‘big’ limitations like slow operating speed, restricted
computing capacity, high power consumption, very large space requirement and limited programming capabilities.
Second Generation Computers (1956-65)
The second generation computers emerged with the transistors being the brain of the computer. They used magnetic cores to construct large random access memories. The increased realiability and availability of large memories gave the way for the development of high level languages. With speedy CPUs and the advent of magnetic tape and disk storage, operating systems came into being. Some of the second generation computers with their area of application are given.

Model Area of application
IBM – 1401 Business
IBM – 1620 Scientific
IBM – 7094 Scientific and Business
CDC – 1604 Scientific
CDC – 3600 Scientific
RCA – 501 Business
UNIVAC – 1108 Scientific and Business
High level languages such as FORTRAN, COBOL, Algol and Snobol etc are developed. Batch operating
systems ruled the second generation.
Third Generation Computers (1966 – 1975)
The advent of microelectronics technology made it possible to integrate large number of circuit elements into
very small surface of silicon known as chips. This technology known as integrated circuits (ICs) is applied in the third generation computers. From small scale integrated (SSI) circuits, technology developed to medium scale integrated (MSI) circuits. The size of main memory reached about 4MB. Magnetic disk technology improved to have a capacity upto 100MBs. The CPUs become powerful with the capacity of carrying out 1 million instructions per second. Some of the mainframe and mini computers developed during this generation are,
Main frame computers Mini computers
IBM – 360 series ICL – 2903
ICL – 1900 series CDC – 1700
IBM – 370/168 series PDP – 11/45
ICL – 2900 series
Honey well model 316 series
Honeywell 6000 series
ICL – International Computers Limited
CDC – Control Data Corporation
PDP – Personal Data Processor
Computers also found place in other areas like education, survey, analysis etc. Time shared operating system was introduced in this generation.
Fourth Generation Computers (1976-Present) Medium scale integrated circuits yielded to Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) circuits. It led to the advent of microprocessor (CPU on a single chip) and marked the beginning of  the fourth generation computers. Semi conductor memories replaced magnetic core memories. The cost of computer came down so rapidly. The faster accessing and processing speeds and increased memory capacity helped in development of much more powerful operating systems.
Many of the mainframe CPU features became part of the microprocessor architecture in 90s. In 1995 the most popular CPUs were Pentium, Power PC etc. Also RISC (Reduced Instruction Set Computer) microprocessors arepreferred in powerful servers for numeric computing and file services.
The hard disks are also available of the sizes upto 20GB. For larger disks RAID (Redundant Array of InexpensiveDisks) gives storage upto hunderes of GB. CDROMs can store upto 1 GB.The computer networks are one of the most popular ways of interacting with computer chains of millions of
users. The computers are being applied in various areas like simulation, visualization, parallel computing, virtual reality, multimedia etc.
Fifth Generation Computers (coming)
The fifth generation computers using magnetic bubble memories and other recent developments are on the way.
They will be based on advances in silicon technology.
The researchers are aiming at developing a machine that can speak simple plain language and able to converse the way the human beings do. For this the concept of Artificial Intelligence is being used.

Summary

FEATURES OF FIRST GENERATION

1. Use of vacuum tubes

2. Big & Clumsy

3. High Electricity Consumption

4. Programming in Mechanical Language

5. Larger AC were needed

6. Lot of electricity failure occured

FEATURES OF SECOND GENERATION

1. Transistors were used

2. Core Memory was developed

3. Faster than First Generation computers

4. First Operating System was developed

5. Programming was in Machine Language & Aseembly Language

6. Magnetic tapes & discs were used

7. Computers became smaller in size than the First Generation computers

8. Computers consumed less heat & consumed less electricity

THIRD GENERATION FEATURES

1. Integrated circuits developed

2. Power consumption was low

3. SSI & MSI Technology was used

4. High level languages were used

FOURTH GENERATION COMPUTERS

1. LSI & VLSI Technology used

2. Development of Portable Computers

3. RAID Technology of data storage

4. Used in virtual reality, multimedia, simulation

5. Computers started in use for Data Communication

6. Different types of memories with very high accessing speed & storage capacity

FIFTH GENERATION COMPUTERS

1. Used in parallel processing

2. Used superconductors

3. Used in speech recognition

4. Used in intelligent robots