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Relocatable CodeProducing an object code, which can be placed to any specific area in memory.
Direct Address Table (DAT): contains offset locations of all direct addresses in the program (e.g., 8080 instructions that specify direct addresses are LDA, STA, all conditional jumps...). To relocate the program, the loader adds the loading point to all these locations.
and DAT Figure 6. Assembler output for a relocatable code.
Example 3: Following relocatable object code and DAT are generated for Example 1.
assembly language memory object code program address in memory
START LDA #0 0000 01 0001 00 0002 00 LDX #0 0003 05 0004 00 0005 00 LOOP: ADD LIST, X 0006 18 0007 00 0008 12 TIX COUNT 0009 2C 000A 00 000B 15 JLT LOOP 000C 38 000D 00 000E 06 RSUB 000F 4C 0010 00 0011 00 LIST: WORD 200 0012 00 0013 02 0014 00 COUNT: WORD 6 0015 00 0016 00 0017 06 END
DAT
Forward and backward references in the machine code are generated relative to address 0000. To relocate the code, the loader adds the new load-point to the references in the machine code which are pointed by the DAT.
Date: 2015-01-11; view: 1311
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