IBM Assembler Question:
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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

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Can we use MVC instruction to move pack field to pack field. which instruction you will use and why?Write the fetch cycle and execute cycle for following instructions:JMPNZ (jump to the given address if the accumulator not equal to zero) RET(return from a subroutine) ADB (add the contents of register B to the accumulator and save result in the accumulator)?