Specifying the Size of a CALL or JMP Instruction in MASM

• Microsoft Macro Assembler for MS-DOS, versions 5.0, 5.1, 5.1a, 6.0, 6.0a, 6.0b

SUMMARY

The PTR operator can be used to specify the size of a register indirect operand for a CALL or JMP instruction. However, the qualifying operators are not NEAR and FAR, but WORD and DWORD. For example, to make a near jump to label xxx, use

   JMP WORD PTR xxx 

MORE INFORMATION

The following example demonstrates how to generate an indirect far call and an indirect far jump in MASM.

Sample Code

; Assemble options needed: none

          .model  large
          .data
jumptable DD      routine1
          DD      routine2

          .code
start:    MOV     ax, @data
          MOV     ds, ax
          CALL    DWORD PTR  jumptable
          JMP     DWORD PTR  jumptable+4
          RET

cseg      SEGMENT word public 'code'
routine1  PROC
          RET
routine1  ENDP

routine2  PROC
          RET
routine2  ENDP
cseg      ENDS

          END     start 

Additional query words: kbinf 5.10 5.10a 6.00 6.00a 6.00b

Keywords :
Version : :5.0,5.1,5.1a,6.0,6.0a,6.0b
Platform :
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