Help with creating a loop in MASM

[revolution9540]

I am programming assembly language (x86) in MASM using Visual Studio 2013 Ultimate. I am trying to use an array to calculate a Fibonacci sequence for n elements using an array. In other words, I am trying to go to an array element, obtain the two elements before it, add those up, and store the result in another array.

I am having trouble setting up the index registers to make this work.

I have my program setup like this:

Code Select Expand

TITLE fibonacci.asm

INCLUDE Irvine32.inc

.data
fibInitial BYTE 2, 3, 4, 5, 6
fibComputed BYTE 5 DUP(0)
fibOne WORD 0
fibTwo WORD 0

.code
main PROC

MOVZX si, fibInitial
MOVZX di, fibComputed
MOV   cl, LENGTHOF fibInitial

L1:
MOV   ax, [si - 1]
MOV   dx, [si - 2]
MOV   bp, ax + dx
MOV   dl, TYPE fibInitial
MOVZX si, dl
MOV   [edi], bp
MOV   dh, TYPE fibComputed
MOVZX di, dl
loop L1

exit
main ENDP
END main



I cannot compile this because of an error message that says "error A2031: must be index or base register" for the line MOV ebp, ax + dx

[dedndave]

i didn't really examine the code....

try this line

Code Select Expand

    lea     bp,[ax+dx]          ;loads BP with AX + DX

don't know how that will go in 16-bit code   :P

on a side note....

you probably don't need to keep the entire array in memory
in fact, if you use registers carefully, you might be able to carry the last 2 values in register

[rrr314159]

hi revolution9540,

Your program won't work as it stands. You don't want two arrays, just one, which will continuously fill up with fib numbers. The array should start like this:

1,2, 0, 0, 0, 0, ...

and end like this:

1,2,3,5,8,13,21,34,55,89,144,233 (next one, 377, won't fit in a byte)

It should look something like this:

Code Select Expand

NUMBER_FIBS_TO_COMPUTE = 10
.data
  fib BYTE 1,2
      BYTE NUMBER_FIBS_TO_COMPUTE dup(0)
.code

main PROC
  lea esi, [fib+2]
  mov cl, NUMBER_FIBS_TO_COMPUTE
@@:
  mov al, [esi-2]
  add al, [esi-1]
  mov [esi], al
  inc esi
  loop @B

; here print out the results or examine them with debugger

exit
main ENDP
END main

I haven't run this, may be some stupid mistake in it, but hopefully u get the idea