ASCII

ASCII (American Standard Code for Information Interchange) is the 
most common format for text files in computers and on the Internet. 
In an ASCII file, each alphabetic, numeric, or special character is 
represented with a 7-bit binary number (a string of seven 0s or 1s). 
128 possible characters are defined.

UNIX and DOS-based operating systems use ASCII for text files. 
Windows NT and 2000 uses a newer code, Unicode. IBM's S/390 systems 
use a proprietary 8-bit code called EBCDIC. Conversion programs allow 
different operating systems to change a file from one code to another.

ASCII was developed by the American National Standards Institute (ANSI).