External data store memory device

TL;DR: In this article, the authors present a device for storing standard software used by the computer and modifying the address portions of the standard software prior to transmission to the computer, using a gating circuit to test whether an address relocation is required.

Abstract: A device for use with a digital computer for storing standard software used by the computer and modifying the address portions of the standard software prior to transmission to the computer The device includes a ROM package containing a ROM within which is stored a standard software subprogram written assuming it is stored at an absolute location in the computer's memory other than its actual location in the computer's memory system Also included in the ROM package is a base register which can be loaded, under control of the operating system software, with an offset value reflecting the difference between the actual starting memory system location of the subprogram stored in the ROM and the assumed absolute starting location of the subprogram Each ROM word includes an extra bit to indicate whether the corresponding data word contains an address requiring relocation As a word is read out of ROM, a gating circuit tests whether an address relocation is required If the test is positive, the gating circuit gates the value in the base register into one input of an adder located on the ROM package, the other input to the adder coming from the data word read out of the ROM The resulting modified data word outputted from the adder is sent to the computer If the ROM output does not indicate that a relocation is required, the gating circuit provides a zero input to the adder so that the adder output reflects the unmodified input from the ROM