Central processor with means for suspending instruction operations

Abstract

A central processor for use in a data processing system that is adapted for processing sequences of characters. Information identifying a string of characters to be examined, including an initial memory location of the first character in the sequence and the total number of characters in the sequence, is placed in working registers of the central processor. Other working registers in the central processor receive information corresponding to a predetermined characteristic, which may be a specific character or information identifying another character string. One of several character string instructions then can be processed. In response to a typical character string instruction, the central processor performs the function defined by the instruction in an iterative fashion as the central processor retrieves successive characters from a memory. During each iteration the central processor tests to determine whether any interruption conditions exist. If one does, the central processor suspends further operations in response to the instruction and services the interruption. When the interruption has been serviced, the central processor again retrieves the suspended instruction and begins processing the character string with the character which would have been processed if the interruption had not occurred.