Computer Knowledge - Exam Oriented
1. Classification of Computers
There are several ways of classifying computers.
I. Depending on the technology used, computers are generally classed as
a. First generation, based on vacuum tubes.
b. Second generation, based on transistors.
c. Third generation, based on small scale integrated circuits.
d. Fourth generation, based on large and very large scale integrated circuits (microprocessor based).
e. Fifth generation, having artificial intelligence.
II. Depending on the principle of working, these are classed as
a. Digital computers�In which mathematical expressions are represented as binary digits and all operations are done using these digits at very high rate. These produce very accurate and precise results,
b. Analog computers�These obtain continuously varying signals and thus depend to a great extent on accuracy of measurement of signal. These are fast and best suited for solving, differential equations.
c. Hybrid computers�These use best qualities of both analog and digital computers.
III. Depending on the size of the computers, these could be classified as:
a. Large scale computer�It may have one or more CPUs for computation. The main storage capacity may be several million characters and the secondary storage capacity ranges in billions of characters. The terminals are connected at several places for interaction with computer by several users. The system can typically work on a number of different programs.
b. Medium. scale and small scale computers�These have same features as large scale but the storage capacity reduces. All these are basically main frame computers, i.e. whole of the CPU is concentrated at one central place. In contrast to this, distributed arrangement is also possible in which case CPU is distributed physically and computations are thus carried out locally at several places.
c. Minicomputer system�It is so small in size that it can be mounted on a rack or put on a table. It is fast in basic operations but has a limited set of instructions. Main memory is of the order of 8 K to 32 K bytes, and the number of input/output devices is also limited. It is frequently dedicated to a specific function.