Development of Computers

Development of Computers – Before the evaluation of computers, the computing aids like the abacus machine and slide rule were available. In the 16th century, a few mechanical systems were developed and further improved. In the 19th century, mechanical system devices for calculators got modified. In such a device, the addition operation was performed with multiple steps. Electronic computers came into the picture in the 20th century after the 1930s. Step by step, the growth of architecture divided the growth of computers into different generations.

Development in Computers

• First Generation (1942-1955)
• Second Generation (1955-1964)
• Third Generation (1964-1975)
• Fourth Generation (1975 onwards)
• Firth Generation (Yet to come)

First Generation (1942-1955)

Vacuum tubes and valves were used in the first generation computers, ENIAC (Electronic Numerical Integrator and Calculator) represents the first generation of computers. It was built during 1943-1946. It used separate memory blocks for code and data. It could perform addition, subtraction, multiplication, division, and square root. The results of any calculation could be obtained on electronic punch cards. It used 20 electronic memory units.

EDVAC (Electronic Discrete Variable Automatic Computer) was the computer of this generation. It was built in 1951. It used a common main memory block of 1k (1024) and used a secondary memory of 20k words for code and data. It used a separate instruction format for the input and output operations 

The IAS (Institute of Advanced Studies) computer was designed and built in 1951. It used a common main memory block of 4k (4096) for code and data. It used the concept of CPU registers so data could be accessed quickly for the instruction. It also used instruction register (IR) and program counter (PC) concepts. It used a magnetic core-based memory for permanent storage of programs. 

The major limitation of such computers was the size. The vacuum tube computers were very large in size (thousands of square feet).

Second Generation (1955-1964)

The semiconductor device, transistor, was invented in 1947 at Bell Labs and by the 1950s had launched an electronic revolution. The use of the transistor defines the second generation of computers. In this generation, computer vacuum tubes were replaced by transistors. The transistor is smaller. cheaper, and dissipates less heat than a vacuum tube. Transistors can be used in the same way as vacuum tubes to construct computers. Unlike the vacuum tube, which requires wires, metal plates, a glass capsule, and a vacuum, the transistor is a solid state device, made from silicon or germanium. PDP-I and NCR-304 were a few computers of the second generation.

Third Generation (1964-1975)

In the 1960s, electronics got revolutionized and started the era of microelectronics. Integrated circuits (ICs) were evolved for electronic circuits. These IC based computers are called third generation computers. IC technology made it possible to integrate a large number of circuit elements like transistors, capacitors, resistors, etc. into a very small surface of silicon, known as ‘chip’. In the third generation, IC technology further reduced the size, power requirements, and cost while increasing the speed, computing power, and reliability. 

IBM-360, PDP-8, PDP-11, CRAY-1 and VAX are some of the examples of third generation computers. SSI (small scale integration logic gates on a single chip), MSI (Medium scale integration more than a hundred logic gates on a single chip), and LSI (Large Scale Integration – more than a thousand logic gates on a single chip) technologies were used to manufacture third generation computers. 

Fourth Generation (1975 onwards)

Advancements in the IC technology created the computers of the fourth generation. VLSI (Very Large Scale Integration) technology of ICs made it possible to integrate more than a thousand logic gates on a single chip. This made it possible to design the complete circuit of central processing unit (CPU) of a computer system within a single chip. These VLSI-IC based computers are called fourth generation computers. The fourth generation computer led to the development of very small but extremely powerful computers. These computers were actually the microcomputers having a microprocessor as their CPU. IBM PC (Personal Computer) and Pentium based computers represent the fourth generation. 

Fifth Generation (Yet to Come)

Scientists are still at work to bring a machine with genuine IQ, the ability to reason logically and with real knowledge of the world. Thus, unlike the last four generations, which naturally followed its predecessor, the fifth generation will be totally different and new. 

All the above-mentioned computer development generations are based on the step-by-step growth in the hardware. Electronic devices used for manufacturing computers of different generations are shown in Fig.