Code Page 437

IBM PC or MS-DOS code page 437, often abbreviated CP437 and also known as DOS-US, OEM-US or sometimes misleadingly referred to as the OEM font, High ASCII or Extended ASCII, is the character set of the original IBM PC. In a more strict sense, this character set was not born as a real code page (in its present sense) but being merely the graphical glyph repertoire available in the ROM of the IBM Enhanced Graphics Adapter (EGA). This bitmapped font is a 8 by 16 pixels-per-character version of the 8 by 14 pixels-per-character font of the IBM Monochrome Display Adapter (MDA) and the 8 by 8 pixels-per-character font of the Color Graphics Adapter (CGA) cards of the original IBM PC. Today, it is still the primary font in the core of any EGA and VGA compatible graphic card, i.e. the text you can see on screen when a PC reboots, before any other font can be loaded from a storage medium, is rendered with this code page. All these display adapters have a basic 80-column text mode, in which every character cell is represented in the video RAM as a single byte (plus an additional byte which carries information about its colour and/or effect), giving 256 possible values for graphic characters.