On 3/15/2013 10:43 AM, John Ehrman wrote:
One reason for the Assembler's not having implemented a fuller set of extended branch mnemonics is that once the original ("incomplete") set wasprovided, many users implemented their own macro-based extensions.Given the decades-long lack of a mechanism to choose between a set of built-in assembler mnemonics and a wide variety of user-implemented mnemonics (not all of which were the same) it seemed safest to stay with the original set. It could be very risky for the assembler to provide built-in extended mnemonics that had slightly different branch masks from those a customer was already using, because programs could behave very differently with no warning or other indication.
It seems to me the most obvious choice for "logical" extended mnemonics would have been to insert the letter 'L' as in Jxxx -> JLxxx. Had I written these macros years ago, I might have created (for example) JLO to branch on overflow (i.e., on 'carry' aka BC 5,xxx) after an ADD LOGICAL. Many developers might have already done this only to have it all stop working when the assembler added JLO to mean "jump long on overflow". So, you might have already silently broken existing macros. -- Edward E Jaffe Phoenix Software International, Inc 831 Parkview Drive North El Segundo, CA 90245 http://www.phoenixsoftware.com/
