ANSI art is a computer art form that was widely used at one time on bulletin board systems. It is similar to ASCII art, but constructed from a larger set of 256 letters, numbers, and symbols — all codes found in IBM code page 437, often referred to as extended ASCII and used in MS-DOS and Unix environments. ANSI art also contains special ANSI escape sequences that color text with the 16 foreground and 8 background colours offered by ANSI.SYS, an MS-DOS device driver loosely based upon the ANSI X3.64 standard for text terminals. Some ANSI artists take advantage of the cursor control sequences within ANSI X3.64 in order to create animations, commonly referred to as ANSImations. ANSI art and text files which incorporate ANSI codes carry the de facto .ANS file extension.