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 common current use are proper supersets of ASCII: these include the ISO 8859 family of encodings, the Windows 1252 code page and the UTF-8 encoding of the Unicode character set.
Each character is assigned a number from 0 to 127, encoded in binary. In addition to the 26 letters of the English alphabet in upper and lower case and all ten digits, many common punctuation symbols are assigned codes, as are control characters, such as backspace, carriage return and linefeed.
Because there are 128 separate codes, each ASCII character can be represented by 7 bits. Since one byte (8 bits) is allocated for each character, this leaves room for one checksum digit to guarantee that the character has not been corrupted in transmission or storage.