A Basic Input-Output System (BIOS) Read-Only Memory (ROM) for a computer system includes a color expansion table, and astorage for storing a computer program for generating an output character represented by bitmapped output scan lines from a correspondinginput character represented by bitmapped input scan lines which have a smaller number of bits than the output scan lines. The input scanlines are each preferably one byte long, with one pixel being represented by one bit The output scan lines are each preferably one wordlong, with each pixel being represented by two bits to provide four selectable colors or shades of grey. The computer program includesinstructions for accessing the expansion table with the input scan lines to obtain corresponding output scan lines. The expansion tableincludes entries which are addressable by a nibble of an input scan line and contain a corresponding byte of an output scan line, andseparate sections for the four colors. A character can be generated once, or a selected number of times, at high speed.
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