Operator Speed and Accuracy with Literal and Combination Codes for Processor Input

Two possible types of keyboard input to a central processor are 1) short codes consisting of combinations of characters extracted from several descriptors, and 2) somewhat longer literal codes where words are spelled letter for letter. The literature indicates that performance should be faster and more accurate with the short combination codes than with the literal type of codes, both codes having equal information content. Three comparisons were made of input speed and accuracy using these two code types with telephone directory listings. Performance was faster with the combination code than with the literal code, both containing 17.1 bits. No difference in performance existed between operators using only the literal code and those selecting and using either the literal code or one of the two shorter codes, each code containing 17.1 to 18.5 bits.