Definition of Octal Number System: The octal number system is the base-8 number system, and uses the digits 0 to 7. That is to say 10octal represents eight and 100octal represents sixty-four.
In the early phase of modern computer development, 6-bit, 12-bit binary words were vastly used. Octal numbers were ideal for abbreviating those words. In the current times, however, 32-bit, 64-bits and even bigger binary words are used in computers.
Base-2 (also called binary) number system uses only two symbols to code information. Most commonly, these two symbols are, 0 and 1.