ASCII

ASCII is a common historical character encoding, designed to represent US English text in digital form. The acronym stands for American Standard Code for Information Interchange. Most of the character encodings in use today are proper supersets of ASCII: these include the ISO 8859 family of encodings, the Windows 1252 code page, and Unicode.

In ASCII, each letter or number on the keyboard is assigned a number from 0 to 127. For example, "A" is assigned the value 65, "B" is assigned 66, and "C" is assigned 67, so the word "cab" would be represented in ASCII as "67 65 66". As well as the 26 letters of the English alphabet and the numbers from 0 to 9, many common punctuation symbols are assigned codes.

ASCII was originally designed to work on mainframe computers, so naturally the first 31 ASCII values were assigned to "control characters", such as carriage return and line feed, which were used to manipulate early teletype machines (a kind of printer). Most of these early ASCII "control characters" have become obsolete, and many modern ASCII implementations do not even bother to assign them, preferring to start the mapping at 32 (ASCII space).

Because there are 128 separate codes, an ASCII character can be represented by a signed char type in the C programming language.