Question
Consider the following program fragment in assembly language: mov ax, 0h mov cx, 0A h doloop: dec ax loop doloop What is the value of ax and cx registers after the completion of the doloop?
The correct answer is
ax = FFF6 h and cx = 0 h
CX starts at 0Ah, or 10. Each LOOP instruction decrements CX and repeats while it is nonzero, so DEC AX executes ten times.
\(AX=(0-10)\bmod 2^{16}=65526=\mathrm{FFF6}_{16}\)
Thus AX = FFF6h and CX = 0000h.
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Important Questions from Machine Instructions and Addressing Modes
- Consider a processor P whose instruction set architecture is the load-store architecture. The instruction format is such that the first operand of any instruction is the destination operand.
Which one of the following sequences of instructions corresponds to the high-level language statement $Z = X + Y$ ?
Note: X, Y, and Z are memory operands. R0, R1, and R2 are registers. - Instruction AAA is used to
- Which of the following is/are part of an Instruction Set Architecture of a processor?
The following language uses mnemonic OP codes
What will be the hexadecimal value in the register ax (32-bit) after executing the following instructions ?
mov al, 15
mov ah, 15
xor al, al
mov cl, 3
shr ax, cl
Codes :
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