Abstract: A method for extracting and replacing Control Block information in an operating system. An extract replace table is provided to permit application programmers to locate and in certain instances replace items contained in operating system Control Blocks. The user of the application program need not know the precise location of information contained in operating system Control Blocks. The extract/replace table will, upon formulating a request for either extracting or replacing Control Block items, find the requested items and read or replace them. Revisions of operating system programs may be made without regard to the new location of control items. The system user will locate and replace Control Block items by addressing the updated extract/replace tables.