DATA PROCESSOR USING READ ONLY MEMORIES FOR OPTIMIZING MAIN MEMORY ACCESS AND IDENTIFYING THE STARTING POSITION OF AN OPERAND

摘要

A data processing system includes a commercial instruction processor for executing decimal alphanumeric instructions uses read only memories in the alignment of the operands. The characteristics of the operands, string or packed decimal as well as the length and position of the most significant decimal digit in a main memory word are specified by data descriptors. The read only memories are responsive to the data descriptor information as well as the instruction being executed to generate signals which specify whether the direction words are read from main memory, high order word first or low order word first, the number of double words in the operand and the location of the least or most significant decimal digit within the word as stored in registers of the commercial instruction processor.