Character generator for visual display devices

Abstract

Binary patterns that define alphanumeric characters for display are stored in a character pattern memory in a size that is smaller than the pattern that will be needed for display purposes. Each such stored character pattern is expanded to the size of a display character pattern, at a time when that character is to be displayed, on a point by point basis of the stored pattern. The expansion of each point in a stored character pattern is accomplished by a relationship that takes into consideration the points surrounding the point to be expanded. When a character requires a binary pattern that is not readily susceptible of this type of expansion, the full display size pattern must be stored in memory. This display size pattern is broken up into a plurality of smaller stored patterns and stored in memory as a plurality of adjacent smaller patterns. In effect, then, two different character pattern sizes are stored in memory. The display size patterns in memory are identified by indicia such as a flag in the first line of the stored pattern, or by a flag in the memory address codes. When such flag is detected, the display size pattern is read from memory, and displayed without being expanded. When such flag bit is not detected, the pattern is read from memory and expanded, prior to display. Use of the word 'display' in this document refers to not only the visual display but also the printer device.