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Digital Computer: Definition and Types
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| Digital Computer: Definition and Types |
The digital computer is a machine that can be programmed to manipulate symbols. It is a powerful tool man has ever created.
Three main components of a digital computer are: CPU (Central Processing Unit), memory, input device and output device as shown in Fig.
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| Block Diagram Of Digital Computer |
The central processing unit is the heart of the digital computer. It consists of a microprocessor that actually executes the instructions organized in programs and informs the computer regarding what is to be done.
The memory is a storage device. It enables the computer to store, data, programs and results.. The input devices generally keyboard and mouse are used to feed programs and data to the computer.
The output devices like display screen, printer etc displays or prints programs, data and/or results according to the instruction given to the computer.
In addition to these components, many other components are required for the operation of these basic components e.g. every digital computer required a bus that transmits data from one part of the computer to the other.
The principal characteristics of a computer are:
- to respond to a specific set of instructions in a well defined manner.
- to execute a program.
- to store and retrieve large amount of data.
Hence, computers can perform complex and repetitive procedures quickly, precisely and reliably.
Modem computers are electronic and digital in nature.
What is a microcomputer ?
A digital computer in which one microprocessor has been provided to act as a CPU is called as a microcomputer.
A desktop computer and portable (or mobile) computers like laptop, notebook, palmtop etc contain one microprocessor to act as a CPU. Hence, they come under the category of microcomputer.
High end powerful servers, mainframe computers, supercomputers etc contain more than one microprocessor to act as a CPU. These microprocessor placed in a CPU of large powerful computer operate in parallel. A computer whose CPU contains more than one microprocessor is called a multiprocessor system.
The computer was developed for complex scientific and engineering calculations and it is a programmable machine. Hence, a computer is defined as a "programmable computing machine".
Besides computation work computers are used for a number of non computational work such as automatic control of industrial equipment, to control process, to measure physical and electrical quantities, to process text, graphics and image, to store information, to display information, to transmit information from one place to another to receive information etc.
Thus, a computer can be defined as a programmable machine that can make calculations, manipulate, measure, store and display information, control process, equipment, machine and appliances, transmit and receive information etc.
Depending on the size and capabilities the computers are classified in various types as shown in given below.
Types of computer
- Mainframes
- Minicomputers
- Microcomputers
1. Mainframes
The largest and the most powerful are called as mainframes.
Their size is very large and can operate at a very high speed.
Mainframes can work with large data words which are typically 64 bits or greater. They have a very large size of memory.
The typical applications of mainframes are, military defence control, business data processing, creation of computer graphics displays.
The fastest and most powerful mainframes are called as supercomputers.
A supercomputer can contain more than one central processors and a memory which is capable of storing 32 million 64 bit words.
2. Minicomputers
Minicomputers are small mainframes. All the features of a mainframe are scaled down to obtain a minicomputer.
Minicomputers operate more slowly and they work with smaller data words (typically 32 bits).
The memory size of minicomputers is also small.
Typical applications of a minicomputer are business data processing, industrial control and scientific research.
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