23. Ambiguous MOVes: PTR and OFFSET

• For the following data definitions

      .DATA
          table1  DW  20 DUP (?)
          status  DB  7  DUP (0)
      .CODE
          mov    EBX,   table1    ; "instruction operands must be the same size"
          mov    ESI,   status    ; "instruction operands must be the same size"
          mov    [EBX], 100       ; "invalid instruction operands"
          mov    [ESI], 100       ; "invalid instruction operands"
  

• The above MOV instructions are ambiguous.

• Not clear whether the assembler should use byte or word equivalent of 100.

• Better:

          mov    EBX, OFFSET table1
          mov    ESI, OFFSET status
          mov    WORD PTR [EBX], 100
          mov    BYTE PTR [ESI], 100