Lecture Coding Schemes

Representing Data English language uses 26 symbols to represent an idea Different sets of bit patterns have been designed to represent text symbols Each set is called a code

Common Codes ASCII Extended ASCII EBCDIC Unicode

ASCII The American National Standards Institute (ANSI) developed a code called ASCII (American Standard Code for Information Interchange) This code uses 7 bits for each symbol 2 7 = 128 different symbols can be defined by the code

Figure 2-5 Representation of the word “BYTE” in ASCII code

Extended ASCII ASCII bit pattern augmented with an extra 0 on the left to represent it in a byte Some manufacturers used it to create an extra 128 symbols however, this attempt has not been very successful

EBCDIC IBM developed a code called EBCDIC – Extended Binary Coded Decimal Interchange Code It uses 8-bit patterns – It can represent up to 256 symbols This code is not used in any computers other than IBM

Unicode To represent symbols belonging to other languages a code with greater capacity was needed Unicode uses 16 bits and can represent up to 2 16 = 65,536 symbols defines codes for characters used in all the major languages written today