On 8/30/2013 12:56 PM, Ward, Mike S wrote:
Hello all, I'm trying to get back into assembler from my old 360 days and I was reading the POO. In the POO under registers it says that there are 16 GP registers available to the program. Ok that sounds good so far, but then it goes on to say that the registers are 64 bits each. Is that true and if it is how can current old assembler programs work in z/OS when they were written for 32 bit registers. Save areas and such would have to be twice as large to hold the registers. Can someone please shed some light on this?
They cleverly made it transparent by adding new non-modal instructions. For example, STMG does a store multiple of the full 64-bit GPRs whereas the old STM instruction only stores the low-order 32 bits of each register--just like in the old days. Therefore, an old program that doesn't know how to manipulate the high halves of the registers should not have an issue... -- Edward E Jaffe Phoenix Software International, Inc 831 Parkview Drive North El Segundo, CA 90245 http://www.phoenixsoftware.com/
