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I'm writing a subroutine display(Z, n, flag), where Z is an int/ string array, n is the length of the array and the flag indicates if Z is an address of string or integer array.

Based on the value of the flag, the subroutine either displays Z as a byte array of length n, displaying each byte as a character, or it displays Z as an integer array.

And here's where the confusion is. I'm having a hard time understanding how to differentiate between the 2 address. I feel like this is something incredibly basic but I just can't seem to figure it out. Any/all ideas would be appreciated!

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  • Integer must be incremented by 4 when indexing. Commented Dec 16, 2015 at 10:40
  • Your question is very ambiguous. Is Z always an array (of either type) or is Z sometimes an integer array and sometimes a single string? Given this ambiguity user @Fifoernik has provided you with a decent answer. Commented Dec 20, 2015 at 18:02

1 Answer 1

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where Z is an int/ string array

If Z is the address of an array of integers, the address points at dwords that contains the actual numerical value of these integers. 

mov ebx, Z
mov eax, [ebx]    ;value of 1st integer
mov eax, [ebx+4]  ;value of 2nd integer

If Z is the address of an array of strings, the address points at a list of addresses that each point at a string in memory.

mov ebx, Z
mov esi, [ebx]    ;address of 1st string
mov al,  [esi]    ;1st character of 1st string
mov al,  [esi+1]  ;2nd character of 1st string
...
mov esi, [ebx+4]  ;address of 2nd string
mov al,  [esi]    ;1st character of 2nd string
mov al,  [esi+1]  ;2nd character of 2nd string

n is the length of the array

n says how many elements there are in these arrays. In the case of an array of strings, the length of an individual string is determined by finding the terminating zero.

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