what are the character codes?

each computer has a set of characters that it uses.in order to transfer these characters into the computer. each one is assigned a number. the mapping of character onto integers is called character codes.when computers are communicating they must use same code otherwise they will not be able to understand one another.for this reason standards have been developed.
e.g.:

1. BCD(binary coded decimal)
2. EBCDIC(extended binary coded decimal interchange code)
3. ASCII(American standard code for information interchange)
4. ISCII(indian standard code for information interchange)