History of computer

Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices.
The various generations of computers an listed below :
(i) First Generation (1946-1954) : In 1946 there was no 'best' way of storing instructions and data in a computer memory. There were four competing technologies for providing computer memory: electrostatic storage tubes, acoustic delay lines (mercury or nickel), magnetic drums (and disks?), andmagnetic core storage.
The digital computes using electronic valves (Vacuum tubes) are known as first generation computers. the first 'computer' to use electronic valves (ie. vacuum tubes). The high cost of vacuum tubes prevented their use for main memory. They stored information in the form of propagating sound waves.
The vacuum tube consumes a lot of power. The Vacuum tube was developed by Lee DeForest in 1908. These computers were large in size and writing programs on them was difficult. Some of the computers of this generation were:
Mark I : The IBM Automatic Sequence Controlled Calculator (ASCC), called the Mark I by Harvard University, was an electro-mechanical computer. Mark I is the first machine to successfully perform a long services ofarithmetic and logical operation. Mark I is the First Generation Computer. it was the first operating machine that could execute long computations automatically. Mark I computer which was built as a partnership between Harvard and IBM in 1944. This was the first programmable digital computer made in the U.S. But it was not a purely electronic computer. Instead the Mark I was constructed out of switches, relays, rotating shafts, and clutches. The machine weighed 5 tons, incorporated 500 miles of wire, was 8 feet tall and 51 feet long, and had a 50 ft rotating shaft running its length, turned by a 5 horsepower electric motor.
1. They were large in size, slow in processing and had less storage capacity.
2.  They consumed lots of electricity and produced lots of heat.
3.  Their computing capabilities were limited.
4. They were not so accurate and reliable.
5.  They used machine level language for programming.
6.  They were very expensive.
Example: ENIAC, UNIVAC, IBM 650 etc
(ii)  Second Generation (1955-1964) : The second-generation computer used transistors for CPU components & ferrite cores for main memory &magnetic disks for secondary memory. They used high-level languages such asFORTRAN (1956), ALGOL (1960) & COBOL (1960 - 1961). I/O processor was included to control I/O operations.
Around 1955 a device called Transistor replaced the bulky Vacuum tubes in the first generation computer. Transistors are smaller than Vacuum tubes and have higher operating speed. They have no filament and require no heating. Manufacturing cost was also very low. Thus the size of the computer got reduced considerably.
It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming language and input and output units were developed. The programming languages such as COBOL, FORTRAN were developed during this period. 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 (51 square feet)
4. The input and output devices were faster.
Example: IBM 1400 and 7000 Series, Control Data 3600 etc.
(iii)Third Generation (1964-1977) : By the development of a small chip consisting of the capacity of the 300 transistors. These ICs are popularly known as Chips. A single IC has many transistors, registers and capacitors built on a single thin slice of silicon. So it is quite obvious that the size of the computer got further reduced. Some of the computers developed during this period were IBM-360, ICL-1900, IBM-370, and VAX-750. Higher level language such as BASIC (Beginners All purpose Symbolic Instruction Code) was developed during this period.  Computers of this generation were small in size, low cost, large memory and processing speed is very high. Very soon ICs Were replaced by LSI (Large Scale Integration), which consisted about 100 components. An IC containing about 100 components is called LSI.
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.  Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) were also developed.
5.  The mini computers were introduced in this generation.
6. They used high level language for programming.
Example: IBM 360, IBM 370 etc.

(iv)     Fourth Generation : 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. Later very large scale Integrated Circuits (VLSIC) replaced LSICs. Thus the computer which was occupying a very large room in earlier days can now be placed on a table. The personal computer (PC) that you see in your school is a Fourth Generation Computer Main memory used fast semiconductors chips up to 4 M bits size. Hard disks were used as secondary memory. Keyboards, dot matrix printers etc. were developed. OS-such as MS-DOS, UNIX, Apple’s Macintosh were available. Object oriented language,C++ etc were developed.
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.
(v)    Fifth Generation (1991- continued) : 5th generation computers use 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. Data flow & EPIC architecture of these processors have been developed. RISC & CISC, both types of designs are used in modern processors. Memory chips and flash memory up to 1 GB, hard disks up to 600 GB & optical disks up to 50 GB have been developed. fifth generation digital computer will beArtificial intelligence.
1. They were large in size, slow in processing and had less storage capacity.
2.  They consumed lots of electricity and produced lots of heat.
3.  Their computing capabilities were limited.
4. They were not so accurate and reliable.
5.  They used machine level language for programming.
6.  They were very expensive.
Example: ENIAC, UNIVAC, IBM 650 etc
(ii)  Second Generation (1955-1964) : The second-generation computer used transistors for CPU components & ferrite cores for main memory &magnetic disks for secondary memory. They used high-level languages such asFORTRAN (1956), ALGOL (1960) & COBOL (1960 - 1961). I/O processor was included to control I/O operations.
Around 1955 a device called Transistor replaced the bulky Vacuum tubes in the first generation computer. Transistors are smaller than Vacuum tubes and have higher operating speed. They have no filament and require no heating. Manufacturing cost was also very low. Thus the size of the computer got reduced considerably.
It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming language and input and output units were developed. The programming languages such as COBOL, FORTRAN were developed during this period. 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 (51 square feet)
4. The input and output devices were faster.
Example: IBM 1400 and 7000 Series, Control Data 3600 etc.
(iii)Third Generation (1964-1977) : By the development of a small chip consisting of the capacity of the 300 transistors. These ICs are popularly known as Chips. A single IC has many transistors, registers and capacitors built on a single thin slice of silicon. So it is quite obvious that the size of the computer got further reduced. Some of the computers developed during this period were IBM-360, ICL-1900, IBM-370, and VAX-750. Higher level language such as BASIC (Beginners All purpose Symbolic Instruction Code) was developed during this period.  Computers of this generation were small in size, low cost, large memory and processing speed is very high. Very soon ICs Were replaced by LSI (Large Scale Integration), which consisted about 100 components. An IC containing about 100 components is called LSI.
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.  Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) were also developed.
5.  The mini computers were introduced in this generation.
6. They used high level language for programming.
Example: IBM 360, IBM 370 etc.

(iv)     Fourth Generation : 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. Later very large scale Integrated Circuits (VLSIC) replaced LSICs. Thus the computer which was occupying a very large room in earlier days can now be placed on a table. The personal computer (PC) that you see in your school is a Fourth Generation Computer Main memory used fast semiconductors chips up to 4 M bits size. Hard disks were used as secondary memory. Keyboards, dot matrix printers etc. were developed. OS-such as MS-DOS, UNIX, Apple’s Macintosh were available. Object oriented language,C++ etc were developed.
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.
(v)    Fifth Generation (1991- continued) : 5th generation computers use 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. Data flow & EPIC architecture of these processors have been developed. RISC & CISC, both types of designs are used in modern processors. Memory chips and flash memory up to 1 GB, hard disks up to 600 GB & optical disks up to 50 GB have been developed. fifth generation digital computer will beArtificial intelligence.