Assembly Language Program Execution Quiz

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Questions and Answers

What is the purpose of the `xchg bx, si` instruction in the provided code?

It exchanges the values of the BX and SI registers. (correct)
It increments the values of the BX and SI registers.
It pushes the values of the BX and SI registers onto the stack.
It copies the value of the BX register into the SI register.

What does the `pusha` instruction do in the provided code?

It pops all general-purpose registers from the stack.
It pushes all general-purpose registers onto the stack. (correct)
It clears all general-purpose registers.
It copies the values of all general-purpose registers into memory.

What is the purpose of the `mov cs, ax` and `mov ds, ax` instructions in the provided code?

They load the value of the CS and DS segment registers into the AX register.
They clear the CS and DS segment registers.
They exchange the values of the CS and DS segment registers.
They load the value of the AX register into the CS and DS segment registers. (correct)

What is the purpose of the `loop1` label in the provided code?

<p>It marks the start of a loop that decrements a byte and increments a word. (C)</p> Signup and view all the answers

What is the purpose of the `sti` and `cli` instructions in the provided code?

<p>They enable and disable interrupts, respectively. (D)</p> Signup and view all the answers

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Study Notes

.text
program main begin
    lea sp, 16
    mov al, 27
    mov ah, 17
    mov dx, 0x3960
    mov cs, ax
    mov ds, ax
    xchg bx, si
    pusha
    call print_numbers
    popa
    int nmi
    jmp short restart
restart:
    sti
    cli
end

print_numbers:
    push ax
    push bx
    push cx
    push dx
    push es
    xor dx, dx
    mov es, dx
    mov bp, sp
    push ds
    push ax
    mov ax, 16*32 + 73
    mov ds, ax
    xor si, si
loop1:
    cmp sp, 80h
    je exit
    dec byte ptr [si]
    inc word ptr [si+1]
exit:
    ret
end