Evolution of Computers

The growth of computer industry started with the need for performing fast calculations. The manual method of computing was slow and prone to errors. So attempts were made to develop faster calculating devices. The journey that started from the first calculating device i.e. Abacus has led us today to extremely high speed calculating devices. Let us first have a look at some early calculating devices and then we will explore various generations of computer.

Abacus

Abacus was discovered by the Mesopotamia’s in around 3000 BC. An abacus consisted of beads on movable rods divided into two parts. (Fig-1) Addition and multiplication of numbers was done by using the place value of digits of the numbers and position of beads in an abacus.

Fig. Abacus

The Chinese further improved on the abacus so that calculations could be done more easily. Even today abacus is considered as an apt tool for young children to do calculations. In an abacus, each row is thought of as a ten’s place. From right to left ,row no-1 represents the one’s column and the second column represents ten’s place.The third column represents the hundred’s place and so on. The starting position of the top beads (representing the value of five) is always towards the top wall of the abacus while the lower beads (representing the value of one) will always be pushed towards the lower wall as a starting position.

Napier’s Logs and Bones

The idea of logarithm was developed by John Napier in 1617. He devised a set of numbering rods known as Napier’s bones through which both multiplication and division could be performed. These were numbered rods which could perform multiplication of any number by a number in the range of 2-9. There are 10 bones corresponding to the digits 0-9 and there is also a special eleventh bone that is used to represent the multiplier. By placing bones corresponding to the multiplier on the left side and the bones corresponding to the digits of the multiplicand on the right, the product of two numbers can be easily obtained.

Fig. Napier’s Log

Pascaline

Blaise Pascal, a French mathematician invented an adding machine in 1642 that was made up of gears and was used for adding numbers quickly. This machine was also called Pascaline and was capable of addition and subtraction along with carry-transfer capability. It worked on clockwork mechanism principle. It consisted of various numbered toothed wheels having unique position values. The addition and subtraction operations was performed by controlled rotation of these wheels.

Fig. Pascaline

Leibnitz’s Calculator

In 1673 Gottfried Leibnitz, a German mathematician extended the capabilities of the adding machine invented by Pascal to perform multiplication and division as well. The multiplication was done through repeated addition of numbers using a stepped cylinder each with nine teeth of varying lengths.

Fig. Leibnitz’s Calculator

Jacquard’s Loom

In order to make the cotton weaving process automatic, Joseph Jacquard devised punch cards and used them to control looms in 1801. The entire operation was under a program’s control. Through this historic invention, the concept of storing and retrieving information started.

Difference engine and Analytical Engine

Charles Babbage, an English mathematician developed a machine called Difference Engine in 1822 which could calculate various mathematical functions, do polynomial evaluation by finite difference and theoretically could also solve differential equations. Thereafter in 1833, he designed the Analytical Engine which later on proved to be the basis of modern computer. This machine could perform all the four arithmetic operations as well as comparison. It included the concept of central processor, memory storage and input-output devices. Even the stored information could be modified. Although the analytical engine was never built that time but Babbage established the basic principles on which today’s modern computers work.Both these great inventions earned him the title of ‘Father of Modern Computers’.

 

Mark 1

In 1944 Prof Howard Aiken in collaboration with IBM constructed an electromechanical computer named Mark 1 which could multiply two 10 digit numbers in 5 seconds. This machine was based on the concept of Babbage’s Analytical engine and was the first operational general purpose computer which could execute preprogramed instructions automatically without any human intervention.

Fig. Mark 1

In 1945, Dr. John Von Neumann proposed the concept of a stored program computer. As per this concept the program and data could be stored in the same memory unit. The basic architecture of the Von Neumann computer is shown in the figure below.

Fig. Von Neumann Computer

According to Von Neumann architecture, the processor executes instructions stored in the memory of the computer. Since there is only one communication channel, the processor at a time can either fetch data or an instruction. That means at one point of time either the data or an instruction can be picked (fetched) from the storage unit for execution by the processor. Hence execution takes place in sequential manner. This limitation of Von Neumann Computer is known as Von Neumann bottleneck. EDVAC (Electronic Discrete Variable Automatic Computer) was the first stored program computer developed in 1952. After the invention of first electronic computer ENIAC (Electronic Numerical Integrator and Calculator) in 1946, the computer technology improved tremendously and at very fast pace.

Generation of Computers

Growth in the computer industry is determined by the development in technology. Each phase/generation of computer development is characterized by one or more hardware/software developments that distinctly improved the performance of the computers of that generation. Based on various stages of development, computers can be divided into different generations.

The First Generation (1942-1955)

The first generation computers used the concept of ‘stored program’ and were characterized by vacuum tubes. A vacuum tube is a delicate glass device that can control and amplify electronic signals. The first generation computers were made using thousands of vacuum tubes and were the fastest calculating devices of their time.

Salient features of First generation computers:

• Used vacuum tubes to control and amplify electronic signals
• Huge computers that occupied lot of space
• High electricity consumption and high heat generation
• Were unreliable since they were prone to frequent hardware failures
• Commercial production was difficult
• They were very costly and required constant maintenance
• Continuous air conditioning was required
• Programming was done in machine language although assembly language also started at the end of this generation Example: ENIAC, EDVAC and UNIVAC
• Note: ENIAC weighed about 27 tons, was of the size 8 feet * 100 feet * 3 feet and consumed around 150 watts of power.

The Second Generation (1955–1964)

In 2nd generation computers, Vacuum tubes were replaced by Transistors. They required only 1/10 of power required by Vacuum tubes. This generation computers generated less heat & were reliable. The first operating system developed in this generation.

Salient Features of Second generation computers:

• Use transistor based technology
• Were smaller and less expensive as compared to first generation
• Consumed less electricity and emitted less heat
• Magnetic core memories and magnetic disks were used as primary and secondary storage respectively
• First operating system developed
• Programming in assembly language and in the later part high level languages were used
• Wider commercial use but commercial production was still difficult
• They also required constant air-conditioning.
• Examples: IBM 1401, IBM 1620, UNIVAC 1108

The Third Generation (1964-1975)

The 3rd generation computers replaced transistors with Integrated circuit known as chip. From small scale integrated circuits which had 10 transistors per chip, technology developed to MSI circuits with 100 transistors per chip. These computers were smaller, faster & more reliable. High level languages invented in this generation.

Salient Features of Third Generation computers:

• Used integrated circuits
• Computers were smaller , faster and more reliable
• Low power consumption and less emission of heat as compared to previous generations
• Examples: IBM 360 series, Honeywell 6000 series

The Fourth Generation (1975 onwards)

LSI & VLSI were used in this generation. As a result microprocessors came into existence. The computers using this technology known to be Micro Computers. High capacity hard disk were invented. There is great development in data communication.

Salient features of Fourth generation Computers

• ICs with LSI and VLSI technology
• Microprocessors developed
• Portable computers developed
• Networking and data communication became popular
• Different types of secondary memory with high storage capacity and fast access developed
• Very reliable ,powerful and small in size
• Negligible power consumption and heat generation
• Very less production cost

Fifth Generation Computers (Present & Beyond)

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come.

Salient features of fifth generation computers:

• Parallel Processing
• Superconductivity
• Artificial Intelligence

Classification of Computers

The computers can be classified based on the technology being used as: Digital, Analog and Hybrid.

Digital Computers

A computer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system. Binary digits are easily expressed in a digital computer by the presence (1) or absence (0) of current or voltage. It computes by counting and adding operations. The digital computers are used in industrial, business and scientific applications. They are quite suitable for large volume data processing.

Digital Computers can be classified on the basis of size and capability as under.

• Super Computer -> The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration. PARAM & Pace are the supercomputer made in India.
• Mainframe Computer -> A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In the hierarchy that starts with a simple microprocessor (in watches, for example) at the bottom and moves to supercomputers at the top, mainframes are just below In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.
• Mini Computer -> A mid-sized computer. In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously. Generally, servers are comes in this category.
• Micro Computers -> These are also known as Personal Computers. These type of digital computer uses a microprocessor (a CPU on a single chip) and include both desktops and laptops. These computers can work on small volume of data, are very versatile and can handle variety of applications.

1. Desktop Computer: a personal or micro-mini computer sufficient to fit on a desk.
2. Laptop Computer: a portable computer complete with an integrated screen and keyboard. It is generally smaller in size than a desktop computer and larger than a notebook computer.
3. Palmtop Computer/Digital Diary /Notebook /PDAs: A hand-sized computer. Palmtops have no keyboard but the screen serves both as an input and output device.

 Analog Computers

An Analog computer is a form of computer that uses continuous physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. These computers measure changes in continuous physical quantities say current and voltage. These computers are used to process data generated by ongoing physical processes. Example: Thermometer, Speedometer, Petrol pump indicator etc.

 Hybrid Computers (Analog + Digital)

These use both analog and digital technology. It has the speed of analog computer and the accuracy of a digital computer. It may accept digital or analog signals but an extensive conversion of data from digital to analog and analog to digital has to be done. Generally the analog components provide efficient processing of differential equations while the digital part deals with logical operations of the system. Hence benefits of both analog and digital computing are readily available. Hybrid Computers are used as a cost effective means for complex simulations.