On 8/30/2013 1:56 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?
Thanks
Yes, it's true. It works because there are several features at work here: * Many old instructions continue to work with just the rightmost 32 bits of registers * Other instructions are sensitive to the current AMODE * Still other instructions are introduced to work with 64-bit registers (or a 64-bit register and a 32-bit register [that is, the rightmost 32 bits of a 64-bit register]) http://www.trainersfriend.com/Assembler_courses/C500descrpt.htm Kind regards, -Steve Comstock The Trainer's Friend, Inc.
