Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!wuarchive!psuvax1!psuvm!CFAAMP!PEPMNT From: PEPMNT@CFAAMP.BITNET (John F. Chandler) Newsgroups: bit.listserv.ibm-main Subject: Re: Base Registers Message-ID: Date: 9 Feb 90 17:11:02 GMT Sender: IBM Mainframe Discussion list Reply-To: IBM Mainframe Discussion list Lines: 13 Approved: NETNEWS@PSUVM Gateway In-Reply-To: SYKLB@NASAGISS.BITNET message of Fri, 9 Feb 90 10:42:24 EDT > I thought that once a base register was declared, > its contents could not be changed (at least so long as any address > references still depended on that base register). Am I wrong? Yes, you were wrong. Base registers are often used for pointing at control blocks in order to map standard DSECT labels onto locations not known at assembly time, and these control blocks often turn out to be members of large classes of similar blocks with the same conceptual mapping. It is therefore often convenient to set up a USING once in a program and just load the base register with the proper value each time you want to look at a different block. Your sample of code is clearly an example of that strategy. John