Radix-64, also known as base64 or ASCII Armor, is a data
encoding scheme whereby
binary-encoded data is converted to
ASCII characters. The only characters used are the upper- and lower-case
Roman alphabet characters (A-Z, a-z), the numerals (0-9), and the "+" and "/" symbols, with the "=" symbol as a special suffix code. The scheme is defined only for data whose original length is a multiple of 8
bits, a requirement met by most computer file formats. The resultant Radix-64 encoded data has a length that is approximately 33% greater than the original data, and typically appears as seemingly random characters.
Radix-64 may be used by computer programs whose output meets the OpenPGP standard, specified in RFC 2440, to permit encrypted data to be sent as ordinary ASCII text through email, without the need to treat the data as an attached file. It appears to have been originally published in RFC 1421.
On the Web
Code at the following site implements a base64 algorithm for use in translating files to/from base64 encoding:
http://base64.sourceforge.net
Here is a copy of the source code (C language) in Wikipedia:
B64.c[?]