Answer :
Final answer:
Option 4 is the correct code snippet that creates a pretest loop and ensures the body of the loop executes exactly five times by setting ECX to 5 and starting with a jump to the loop condition check.
Explanation:
The question is about identifying which code snippet ensures that a pretest loop executes the body of the loop exactly five times. A pretest loop checks its condition before the body executes. In assembly language with a loop instruction, the loop uses a counter, generally the ECX register, to determine how many times to run. The loop instruction decrements the counter and continues until the counter reaches zero.
Looking at the options provided, we have to find the one where ECX is set to a value such that the body of the loop runs five times before the loop exits. For this to happen, ECX should be set to 5 initially, as the 'loop' instruction decrements ECX and then checks if it is zero.
Option 1 sets ECX to 5, but it has an unnecessary jump (jmp to Label 2), which is irrelevant since no condition is checked before the loop starts.
Option 2 sets ECX to 6 and also deviates directly to the addition part without checking the condition, so the loop runs six times.
Option 3 sets ECX to 6 and executes the 'add' instruction after the first unconditional jump to Label 2, which would result in the body executing six times.
Option 4 seems correct as it sets ECX to 5 and jumps to Label 1, which is the start of the loop condition check, thereby satisfying both criteria: the loop is a pretest, and the loop body is executed exactly five times.
