80-column text mode
80-column text mode is part of the category Display Hardware Supported.
About Text Modes
In a text mode the pixels that make up the display image cannot be set individually. Instead, the screen is broken up into character cells where each cell can be set to one of the available predefined letters or symbols. This limitation allows high resolution text while needing less memory and allows faster screen updates. Since it was not possible to have control over individual pixels, the only type of graphics that could be displayed was ASCII art. The number of colors available, the display resolution, and the font used for the characters depended on what display adapter and monitor were being used; the font was typically stored in ROM and could not be modified by software (although some cards did allow font modifications).
IBM Monochrome Display Adapter (MDA)
The IBM Monochrome Display Adapter was introduced in 1981 along with the IBM PC. The only video mode available with the card was an 80x25 text mode. The low cost of the card along with the high quality text it displayed made the card a popular choice for businesses.
With the IBM MDA adapter each character it displayed could be regular intensity, high intensity, underlined, blinking, or inverse; it was also possible to combine some of these attributes (for example, to achieve high intensity underlined text). The display resolution of 720x350 with characters each using 9x14 pixels provided very sharp text for the time and was easier to read than 80 column text on a CGA card. The 256 characters available were all part of a set known as code page 437; this set of characters included standard alpha-numeric characters, accented letters, special symbols, and some simple graphical pieces such as boxes and borders.
The original IBM MDA card also included a parallel printer port eliminating the need for a separate card for printing.
In 1984, the Hercules Monochrome adapter was released which featured an MDA compatible text mode, but also allowed a graphics mode where individual pixels could be set.
See also: 40-column text mode.
IBM Color Display Standards
While any IBM computer could display 80x25 column text, PC's with a CGA card connected to a composite monitor or t.v. made the text very difficult to read, especially with color enabled, due to composite video artifacting. Later graphics standards, such as VGA, also provided text modes with more lines, such as 80x43 and 80x50, however these were very rarely used.
Apple 80-Column Text Card
The Apple 80-Column Text Card allowed Apple IIe computers to display 80 column text instead of the usual 40 column text that was available. The card came in two varieties; the Standard 80-Column Text Card featured an additional 1 KB of memory which was necessary in order to display 80 column text. The Extended 80-Column Text Card featured an additional 64 KB of memory available for programs which made available not only 80 column text but also the Double Hi-Res graphics mode. Double Hi-Res graphics were not available on the Apple IIe with a Revision A motherboard; those systems did not support bank switching which was required to access the additional memory for Double Hi-Res graphics. The Apple IIc featured the capabilities of the Extended 80-Column Text Card built in so it could display both 80 column text and Double Hi-Res graphics without the need for any additional boards; Apple II computers prior to the IIe did not support any options for the advanced features.
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|IBM Monochrome Display and Printer Adapter|