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Using the Location Counter

2. Referencing the Location Counter. The location counter (in the PSW) always points at the next instruction.Can directly reference the location counter in commands, using *E.g., * 8 would refer to 8 bytes past the current location counter.Can actually use the location counter directly for bra

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Using the Location Counter

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    1. 1 Using the Location Counter

    2. 2 Referencing the Location Counter The location counter (in the PSW) always points at the next instruction. Can directly reference the location counter in commands, using * E.g., * + 8 would refer to 8 bytes past the current location counter. Can actually use the location counter directly for branching...

    3. 3 Referencing the Location Counter CLI 0(R1), C' ' BE *+12 LA R1,1(R1) B *-12 … add arrows??? Check address

    4. 4 Referencing the Location Counter Advantage: avoids cluttering program with unnecessary labels. Disadvantage: must be very careful about later inserting commands that would change the spacing between the referenced locations. Unless you have a very good reason to use this, don’t.

    5. 5 ORG Command Doesn't just reference location counter value; actually alters it. Allows you to reuse/redefine areas of storage (like REDEFINES in COBOL). ORG command at end is highly recommended to reset to the location counter again; omitting this is a common cause of problems.

    6. 6 ORG Command location counter 000280 INPUT DS CL80 ORG INPUT 000280 TYPE DS CL1 000281 NAME DS CL40 0002A9 STREET DS CL39 ORG INPUT+1 (or NAME) 000281 CITY DS CL20 000295 STATE DS CL20 0002A9 ZIP DS CL10 0002B3 CNTRY DS CL20 ORG important! 002D0 ...…

    7. 7 ORG Command

    8. 8 ORG Command location counter 000280 INPUT DC CL80 ORG INPUT 000280 TYPE DS CL1 000281 NAME DS CL40 0002A9 STREET DS CL39 ORG INPUT+1 (or NAME) 000281 CITY DS CL20 000295 STATE DS CL20 0002A9 ZIP DS CL10 0002B3 CNTRY DS CL20 ORG 002D0 ...…

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