Computer Knowledge - Exam Oriented
1. Binary Number System
Computer use electrical/electronic/magnetic devices to handle the information and these devices can only indicate two states or conditions. All information is represented within the computer by presence or absence of a pulse or voltage For this reason computers use binary number system which has only two digits 0 (no pulse) and 1 (pulse is present). Various symbols (alphabets A to Z, digits 0 to 9 and certain special characters) are represented in the computer by combinations of bits, each symbol being represented by a unique pattern of eight bits. By using six bits, it is possible to represent 64 alphanumerical character set, but most computers use eight bits.
In our day to day working, we use denary system, i.e. the system using ten different characters from 0 to 9. Numbers larger than 9 are expressed using same characters but using further columns. In two columns we can count upto one hundred numbers, in 3 columns upto one thousand numbers.
On the other hand, digital computer operates on binary system. Such a system operates by two characters 0 and 1. Exactly as in denary system, in binary system also bigger numbers are expressed by using same characters 0 and 1 in other columns. For instance 1 is represented by 1, and for representing 2 we make use of next column and shift to the left one column and write 1 in new column and 0 in original, thus 2 is written as 10. Similarly 3 is written as 11, 4 a 100, 5 as 101, 6 as 110, 7 as 111, 8 as 1000, 9 as 1001, and 10 as 1010 (read one zero one zero and not as one thousand and ten). It would be noted that when we add 1 and 1, we write 0 and carry over 1 to next column, It would be noted, presence of 1 in various columns is equivalent to as follows : in column 1�1, in column 2�2, in column 3�4, in column 4�8 and so on.
There are various reasons to use a binary system in computers instead of denary system.
(i) This system is ideal for coding purposes for the computer because of the two state nature of the electrical components, i.e. a transistor conducting or non-conducting, an electrical pulse present or not present, magnetic material magnetized in one direction or the other.
(ii) It is difficult to maintain a device capable of recognizing ten characters in a sufficiently reliable state of operation. On the other hand it is very easy to have a highly reliable device which is either �on� representing 1 or �off� representing 0.
(iii) It is much simpler.
(iv) Operations are performed most rapidly.
(v) Reliability of operation can be ensured.
Its only disadvantage is the need of many more digits and columns to express given numbers.