There are two other number systems which are used in digital computers.
(i) Octal System and
(ii) Hexadecimal System.
Numbers of these systems possess simple relations with the binary numbers. Although binary arithmetic is simple and easy to manipulate, the binary representation of decimal number is lengthy and for this reason, the use of octal and hexa-decimal numbers, which can be expressed as strings of bits, are preferred in some cases.
Uses of Octal and Hexa-decimal Numbers:
The preceding discussion shows that octal and hexa-decimal numbers can be easily converted to binary numbers and vice-versa. For this reason, octal and hexa-decimal numbers are useful in representing binary numbers in a compact form. Computer memory is often specified with numbers represented in groups of 8 bits which makes hexa-decimal system particularly useful at this stage.
Both octal and hexa-decimal number system are used for input-output operations and for storing data and information in memory. All arithmetic operations, however, are made in the binary system and hence ALU of the computer uses only binary systems.