Question

What will be the final values of CX and DX when the following code executes?

.data
array sword 8,2,3,5,-4,6,0,4

.code
mov cx,1
mov esi,2
mov ax,array[esi]
mov bx,array[esi+4]
cmp ax,3
jae l2
cmp bx,4
jb l1
jmp l3
l1: mov cx,4
l2: mov dx,5
jmp l4
l3: mov dx,6
l4:

a) CX = 1, DX = 5
b) CX = 4, DX = 6
c) CX = 1, DX = 6
d) CX = 4, DX = 5

Answer 1

The final values of the CX and DX registers after executing the provided assembly code will be CX = 1 and DX = 5. The program sets CX to 1, compares values from an array, and changes DX to 5 after determining AX is equal to 3.

Step-by-step explanation:

The code provided is an assembly language program that manipulates registers based on certain conditions. Initially, CX is set to 1, and DX is uninitialized. The program moves through data located at specific offsets from the array address in the ESI register. Comparisons are made to determine the final values of CX and DX registers.

After setting CX to 1 and placing the third element of the array (with an assumed zero-based index) into AX, and the fourth element into BX, it compares AX and BX to 3 and 4 respectively, branching to different labels depending on the outcome. jae (jump if above or equal) and jb (jump if below) instructions are used to decide the flow.

Since AX contains a 3, the first comparison jae will pass (as 3 is equal to 3), hence the program will follow l2, setting DX to 5. The second comparison is not reached due to the jump to l2, so CX remains at 1. Therefore, the final values of these registers will be CX = 1 and DX = 5.