ASCII + others

ASCII codes

Most computer systems use a coding system known as ASCII (American Code for Information Interchange) or something very similar to it. All input to and from the computer is via these codes. For instance, when you press a capital “A” on the keyboard a binary pattern of 01000001 (65 in decimal) is produced. A “B” would be the next binary pattern up. ie 01000010 (66 in decimal). Most confusing is the fact that the number 0 is represented by 00110000 (48 in decimal) and so on.

Many ASCII codes are historical. For instance ASCII code for 7 would originally have produced a bell ring on teletypes, on more modern computers this is translated as a little “beep”.

There is another standard known as ANSI which is used by some systems. Many of the codes are exactly the same as ASCII, eg alphabetic characters.

Extended Binary Coded Decimal Interchange Code (EBCDIC)

This was another method of coding data invented by IBM in the early 1960’s from it’s punched card data format. To call it a standard is not correct since there are at least 6 different formats and is not used by anyone but IBM. In the computer industry it was suspected that IBM developed it as a way of “locking in” existing customers into it’s own technology. This should not be mentioned on a modern computing syllabus – but it is.

Unicode

The original ASCII was only an 8-bit standard and, not surprisingly, biased towards the English (or American) speaking world. All the other character sets for other countries were largely ignored. To get around this a 16-bit character set standard, designed and maintained by non-profit consortium was developed.

Originally Unicode was designed to be universal, unique, and uniform, i.e., the code was to cover all major modern written languages (universal), each character was to have exactly one encoding (unique), and each character was to be represented by a fixed width in bits (uniform).