American Standard Code for Information Interchange
Like other character representation computer codes, ASCII specifies a correspondence
between digital bit patterns and the glyphs (i.e., symbols) of a written language. This
allows digital devices to communicate with each other and to process, store, and
communicate character-oriented information
Except for a few of the ASCII control characters that prescribe some elementary line-
oriented formatting, ASCII does not define any mechanism for describing the structure
or appearance of text within a document.
ASCII is, strictly, a seven-bit code, meaning it uses patterns of seven binary digits (a
range of 0 to 127 decimal) to represent each character. In seven-bit ASCII encoding, the
eighth bit is commonly used as a parity bit for error checking on communication lines or
for other device-specific functions.
There are 95 printable ASCII characters, numbered 32 to 126 (decimal) in the original code.
Structural features
The digits 0–9 are represented with their values in binary prefixed with 0011 (this means
that converting BCD to ASCII is simply a matter of taking each BCD nibble separately
and prefixing 0011 to it).
Lowercase and uppercase letters only differ in bit pattern by a single bit, simplifying
case conversion to a range test (to avoid converting characters that are not letters) and a
single bitwise operation. Fast case conversion is important because it is often used in case-
ignoring search algorithms.
In contrast with EBCDIC, the lowercase and uppercase letters each occupy 26 consecutive
positions.
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