Variable character spacing matrix for proportional spacing printing systems

摘要

The aesthetic characteristics of adjacent characters are used to enhance the quality of output in a proportional spacing printer and to provide right margin justification for composing. Spacing between characters is determined on the basis of the character being printed and the preceding character already printed on the page. An intercharacter displacement memory contains a list of ideal spacing for all combinations of characters to be printed. As each character is typed, it and the previously stored preceding character address the intercharacter displacement memory. The output of the intercharacter displacement memory is the ideal value of escapement for this combination of characters and font style. The printer positions the print head prior to printing the next character, rather than positioning the print head after the previous character is printed. Line ending decisions for composing are eliminated during initial and final typing of a document by adding to the intercharacter displacement memory recommendations for altering the ideal spacing between characters, where aesthetically possible, to eliminate the need for line ending hyphenation. During initial keying, escapements for adjacent pairs of characters are totaled in a memory for ideal, shortest (tight), and longest (loose) recommended escapements. The line is automatically terminated within the justification range by a carrier return function based on the escapement totals and the selected right margin. Final playout of the page from memory alters the intercharacter escapements from the ideal values to either longer or shorter escapements depending on whether the line is to be lengthened or shortened.