16. Register Operands

Register operands refer to data stored in registers. The following examples show typical register operands:

        mov     bx, 10          ; Load constant to BX
        add     ax, bx          ; Add BX to AX
        jmp     di              ; Jump to the address in DI

An offset stored in a base or index register often serves as a pointer into memory.

You can store an offset in one of the base or index registers, then use the register as an indirect memory operand. For example:

        mov     [bx], dl ; Store DL in indirect memory operand
        inc     bx       ; Increment register operand
        mov     [bx], dl ; Store DL in new indirect memory operand

This example moves the value in DL twice to 2 consecutive bytes of a memory location pointed to by BX.

Example shows that changing BX register causes it to point to a different location in memory.