1. Binary Coded Decimal (BCD) code:
In this code each decimal digit is represented by a 4-bit binary number. BCD is a way to express each of the decimal digits with a binary code. In the BCD, with four bits we can represent sixteen numbers (0000 to 1111). But in BCD code only first ten of these are used (0000 to 1001). The remaining six code combinations i.e. 1010 to 1111 are invalid in BCD.
2. EBCDIC:
EBCDIC (Extended Binary Coded Decimal Interchange Code is a binary code for alphabetic and numeric characters that IBM developed for its larger operating systems. In an EBCDIC file, each alphabetic or numeric character is represented with an 8-bit binary number. 256 possible characters (letters of the alphabet, numerals, and special characters) are defined.
3. ASCII code: ASCII (**** Standard Code for Information Interchange) is the most widely used coding system to represent data. ASCII is used on many personal computers and minicomputers. ASCII is a 7-bit code that permits 27 = 128 distinct characters. The 128 different combinations that can be represented in 7 bits are plenty to allow for all the letters, numbers and special symbols. An eight bit was added. This allowed extra 128 characters to be represented. The extra 128 combinations are used for symbols such as , , è, , ®, , etc.
