Answer to Question #150844 in Assembler for Rakibul

Question

Show how array data can be located using base-plus-index addressing.

Answer 1

Base-Plus-Index Addressing

This type of addressing uses one base register (BP or BX), and one index register (DI or SI) to indirectly address memory. The base register holds the beginning location of a memory array, while the index register holds the relative position of an element in the array.

 

Example. Size of array elements=double word.

.data

arrayZero DWORD 10 DUP(?)

 

.code

           xor eax, eax                           ; eax=0

mov ebx, offset array            ; ebx = base address of arrayZero

           mov edi, 0                             ; edi = index

           mov [ebx+edi], eax               ; write 0 to arrayZero[0]

           add edi, 4                              ; next item of arrayZero

           mov [ebx+edi], eax               ; write 0 to arrayZero[1]