IBM PC or MS-DOS Codepage 437, also known as DOS-US or OEM-US, is the original character set of the IBM PC, from 1981. The character set is laid out like this:

It is based on ASCII, with the following modifications:

• The C0 control range (0x00-0x1F hex) is mapped to graphics characters. The codes can assume their original function as controls (as they still do--typing "echo", space, control-G and then Enter causes the PC speaker to emit a beep, even on the command prompt on Windows XP), but in display, for example in a screen editor like MS-DOS edit, they show as graphics. The graphics are various, such as smiling faces, card suites and musical notes. Code 0x7F, DEL, similarly shows as a graphic (a house).

• The high-bit range, 0x80-0xFF, is mapped to various symbols: a few European characters (accented Latin vowels, etc) in no particular order and not sufficient for representation of most Western European languages, box-drawing characters, mathematical symbols and a few Greek letters.

The repertoire of CP437 was taken from the character set of Wang word-processing machines, as explicitly admitted by Bill Gates in the interview of him and Paul Allen in the 2^nd of October 1995 edition of Fortune Magazine:

"... we were also fascinated by dedicated word processors from Wang, because we believed that general-purpose machines could do that just as well. That's why, when it came time to design the keyboard for the IBM PC, we put the funny Wang character set into the machine--you know, smiley faces and boxes and triangles and stuff. We were thinking we'd like to do a clone of Wang word-processing software someday."

CP437 is inadequate for internationalisation, as it lacks characters necessary for some languages, such as À (capital A with grave) for French, and has only a few Greek letters. Later MS-DOS character sets, such as CP850 (DOS Latin-1), CP852 (DOS Central-European) and CP737 (DOS Greek), filled the gaps for international use while still being nearly compatible with CP437 by retaining the box-drawing characters. All CP437 characters are in Unicode and in Microsoft's WGL4 character set, therefore in most of the fonts on Microsoft Windows, and also in the VGA font of Linux, and the ISO 10646 fonts for X11.

Implementors of mapping tables to Unicode should note that CP437 unifies some characters: 0xE1 is both the German sharp S (U+00DF) and the Greek lowercase beta (U+03B2); 0xE4 is both the n-ary summation sign (U+2211) and the Greek uppercase sigma (U+03A3); 0xE6 is both the micro sign (U+00B5) and the Greek lowercase mu (U+03BC); 0xEA is both the Ohm sign (U+2126) and the Greek uppercase omega (U+03A9); and 0xEE is both the element-of sign (U+2208) and the Greek lowercase epsilon (U+03B5).

See also

• ASCII
• ASCII art
• ANSI art

External link

• Microsoft Code Page 437 reference chart (http://www.microsoft.com/globaldev/reference/oem/437.htm)