Historical development of computers can be traced back to the time human beings were struggling to invent non electronic tools that would simplify arithmetic such as Abacus and Napier Bones.
Abacus
An abacus was a Chinese counting instrument which dates back to 3000 BC. The abacus has bead-like parts that move along rods.
Napier bones
Napier bone was developed by a Scottish mathematician known as John Napier. It helps in multiplication and division
The analytical engine
The analytical engine was designed by an English mathematician known as Charles Babbage in 1832. The engine is recognized as the first real computer and Babbage became the father of computing.
Electronic computers
Electronic computers are classified into five generations depending on the technology used to develop them
First generation computers (1940s – 1958)
First generation computers were very large and used thousands of electronic gadgets called vacuum tubes or thermionic valves. These computers consumed a lot of power, emitted a lot of heat and constantly broke down.
Examples of first generation computers are Electronic Numeric Integrator and Calculator
(ENIAC) and the Electronic Discrete Variable Automatic Computer (EDVAC)
Second generation computers (1958 – 1964)
Second generation computers used tiny solid state electronic devices called transistor that were very much smaller than the vacuum tubes. They produced less heat, were much faster, smaller in size and more reliable than those made of vacuum tubes. Examples of second generation computers include IBM 1401, IBM 7070, UNIVAC 1107, ATLAS LEO Mark III and Honeywell 200.
Third generation computers (1964 – 1970)
Third generation computers used electronic devices called Integrated Circuits (ICs). An IC consists of thousands of small transistor circuited fixed on a semiconductor called a silicon chip.
These computers emitted less heat, were smaller in size and were easier to program, use and maintain compared to previous generations. Examples of third generation computers include smaller and less expensive minicomputers such as IBM 360 and ICL 19000 series
Fourth generation computers (1970 to present)
These computers also used Integrated circuits; however more technological improvement was done on the silicon chip design by compressing more tiny circuits and transistors onto even smaller space.
This design produced Large Scale Integrated (LSI) and Very Large Scale Integrated (VLSI) circuits which were used in the innovation and technological development of the brain of computer called the microprocessor.
Fourth generation computers are characterized by very low emission of heat, smaller in size and easier to use and maintain. Examples of fourth generation computers include IBM 370, IBM 4300, Honeywell DPS-88 and Burroughs 7700.
Fifth generation computers
In this generation fall today’s computers that have very high processing power and speed than their predecessors. The size of these computers is increasingly becoming smaller.
These computers have special instruction sets that allow them to support complex program that mimic human intelligence often referred to as artificial intelligence.
Fifth generation computers are characterized by artificial intelligence, connectivity to internet, superior hardware and software and are very small in size
CLASSIFICATION OF COMPUTERS
Computers can be classified according to physical size, purpose and functionality
Classification according to physical size
Based on physical size, computers can be classified in four main groups
Supercomputers
Mainframe computers
Minicomputers
Microcomputers
Supercomputers
Supercomputers are the fastest, largest, most expensive and powerful computers. They may be described as giant computers. Supercomputers are
able to perform many complex operations in a fraction of a second. Because of its weight, a supercomputer is kept in a special room. Due to their huge processing power, supercomputers generate a lot of heat therefore special cooling systems are required. Sometime the whole CPU is immersed in an aquarium like tank containing liquid fluorocarbon to provide cooling.
Supercomputers are mainly used for scientific research, which requires enormous calculations. Other uses include aerodynamic design and simulation, petroleum research, defense and weapon analysis. Supercomputers are mainly found in developed countries such as USA and Japan where they are used for advanced scientific research such as nuclear physics.
Mainframe computers
Mainframes are less powerful and less expensive than supercomputers. They are said to be big in size. They are used for processing data and performing complex mathematical calculations. They have a large storage capacity and can support a variety of peripherals.
Mainframes are able to handle all kinds of problems whether scientific or commercial. They are mostly found in government agencies, big organizations and companies such as banks, hospitals and airports which have large information processing needs.
Minicomputers
A minicomputer resembles the mainframe but is slightly smaller. It is referred to as a small-scale mainframe computer. A minicomputer supports fewer peripheral devices and is not as powerful and fast as the mainframe computer. It was developed as a cheaper alternative to the mainframes for smaller organizations.
They are used mainly in scientific laboratories, research institutions, engineering plants and places where processing automation is required. They are well adapted for functions such as accounting, word processing, database management and specific industry applications.
Microcomputers
A microcomputer is the smallest, cheapest and relatively least powerful type of computer. It is called microcomputer because its CPU is called a microprocessor, which is very small compared to that of minicomputers, mainframe and supercomputers.
Microcomputers are commonly used in training and learning institutions, small business enterprises and communication centres.
Types of microcomputers
Desktop computer
A desktop computer is designed to be placed on top of an office desk.
Notebook or laptop computer
It is a portable convenient for mobile users.
Personal Digital Assistant (PDA)
It is small enough to fit in the pocket
Classification according to purpose
Computers can be classified according to the tasks they perform either as general purpose or special purpose computers.
General purpose computers
General purpose computers have been designed to be able to perform a variety of tasks when loaded with appropriate programs. They are the most common types of computers in use today. Their flexibility enables them to be applied in a wide range of applications like, document processing, performing calculations, accounting, data and information management.
Special purpose computers
Special purpose computers are designed to serve a specific purpose or to accomplish one particular task. Such computers can perform no other task except the one they were meant to do. Examples of such computers include robots, mobile phones, and electronic calculators. Since special purpose computers are dedicated to a single task, they can perform the task quickly and very efficiently.
Classification according to functionality
Computers can be classified into three types according to the type of data they process. Data can be in discrete or in continuous form.
Digital computers
Digital computers process data that is discrete in nature. Discrete data also known as digital data is usually represented using a two-state square waveform.
Analog computers
These are computers that process data that is continuous in nature. Continuous data also known as analog data is usually represented using a continuous waveform. Analog computers are used in manufacturing process control like monitoring and regulating furnace temperatures, pressures etc. They are also used in other applications like in weather stations to record and process physical quantities e.g wind, cloud speed, temperature etc.
Hybrid computers
Hybrid computers are designed to process both analog and digital data.
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