PURPOSE: To transform a pixel matrix(PM) between the formats of different numbers of bits per pixel by transforming the PM to the format of (m) bits through a transformation table and storing it in a display buffer.

CONSTITUTION: A display character 32 is indicated by a PM 32 composed of a row 33 of 8 pixels and a column 34 of 14 pixels. A character font table 22 of one bit per pixel contains 256 pieces of character expressions. Any specified PM is selected out of this table by a character code byte 26 stored in a text address 31 inside a text code buffer 21. An attribute byte 27 is stored in that buffer as well. The most significant bit of the attribute byte designates a foreground pixel color 28 and four least significant bits designate a background pixel color 29. The PM is processed through a transformation table 23 and transformed to the format of 4 bits. That expression is stored in an APA display buffer 25 from the head of an APA display buffer address 30.