Assembler IBM 370

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vidhya

Assembler IBM 370

Post by vidhya » Thu Mar 16, 2006 1:45 pm

Where can I find IBM 370 assembler tutorials -?
What is R-MOde, A-mode

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arrbee
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RMODE, AMODE

Post by arrbee » Fri Mar 17, 2006 10:28 am

There are a number of modes, attributes, and properties which programs may possess which affect the way they are handled by program management and other areas of MVS.

Each program has an addressing mode (AMODE) and residency mode (RMODE) associated with it at link-edit time. The AMODE can be 24, 31, or ANY, and determines whether the program runs in 24-bit addressing mode or 31-bit addressing mode when it is executed. Many programs from the days of MVS Version 1 still execute in 24-bit mode, but programs which need to address storage above the 16 megabyte line must execute in 31-bit mode. During execution, the mode can be changed using the BSM or BASSM instructions, but it is more common for each program to execute in one mode only - the initial mode is set by the fetch process depending on the AMODE of the program. At any time, the current mode is indicated by the high-order bit of the next instruction address in the PSW, which is 1 in 31-bit mode and 0 in 24-bit mode.

Similarly, each program is assigned a residency mode (RMODE) at link-edit time, which determines whether FETCH will load it below or above the 16 megabyte line. The RMODE can be 24 or ANY. With RMODE = 24, a program will always be loaded below the 16 megabyte line, and with RMODE = ANY, it may be loaded above or below, depending on the AMODE of the caller.
http://cbttape.org/~jmorrison/s370asm/h ... tents.html

HTH.
Arr Bee
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?My joy in learning is partly that it enables me to teach? - Seneca(Roman philosopher, mid-1st century AD)

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