IBM Assembler Question: Download Questions PDF
How to initialize 20,000 bytes in the Assembler?
Answer:
since the machine-code for MVC moves up to 256 bytes, you would need to do a series of MVCs to initialize 20000 bytes. this requires that you maintain a register or two to keep track of how far you've progressed through initialization.
possibly, you could get MVCL to do it; i've never tried...
MVCL uses 2 sets of even-odd pairs of registers to do the move.
you specify source address, destination address, length of source, length of destination, and fill character in the registers. the fill-character goes into the high order byte of (I THINK...) the destination length register (in this case r4)
l r4,=f'20000'
l r6,=f'20000'
la r7,source_field
la r5,dest_field
mvcl r4,r6
possibly, you could get MVCL to do it; i've never tried...
MVCL uses 2 sets of even-odd pairs of registers to do the move.
you specify source address, destination address, length of source, length of destination, and fill character in the registers. the fill-character goes into the high order byte of (I THINK...) the destination length register (in this case r4)
l r4,=f'20000'
l r6,=f'20000'
la r7,source_field
la r5,dest_field
mvcl r4,r6
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