Basic Principle of Digital Communication-1

A computer uses the binary numbering system, which has only two digits, 0 and 1. Any number can be represented by a string of these digits, known as bits (from binary digit).

For example, the decimal number 5 is equal to the binary number 101.
As a bit can have only two values, it can be represented by a voltage that is either on (1) or off (0). This is also known as logical 1 and logical 0. Typical values sed in a computer are 0 V for logical 0 and +5 V for logical 1, although it could lso be the other way around i.e. 0 V for 1 and +5 V for 0. A string of eight bits is called a ‘byte’ (or octet), and can have values ranging from 0 (0000 0000) to 25510 (1111 11112). Computers generally manipulate data in bytes or multiples of bytes.

Programmers use ‘hexadecimal’ notation because it is a more convenient way of defining and dealing with bytes. In the hexadecimal numbering system, there are 16 digits (0–9 and A–F) each of which is represented by four bits. A byte is therefore represented by two hexadecimal digits.

A ‘character’ is a symbol that can be printed. The alphabet, both upper and lower case, numerals, punctuation marks and symbols such as ‘*’ and ‘&’ are all characters. A computer needs to express these characters in such a way that they can be understood by other computers and devices. The most common code for achieving this is the American Standard Code for Information Interchange (ASCII).