Tracing a program: one row per instruction actually run

In a high-level language you read code top to bottom. An assembly program does not work like that: JMP, JPE and JPN send the processor backwards and forwards, so the same instruction runs several times and others are skipped.

A trace table records the path the processor actually took. That is the whole point: one row per instruction executed, in the order it runs.

If a loop runs three times, the loop's instructions appear in the table three times. If a jump is not taken, the next row is simply the following instruction.

1. Write the address first. The left-hand column is the address of the instruction, so the examiner can see the jump immediately. Do not renumber rows.
2. Record only what changed. A blank cell means "unchanged". Copying an unchanged value into every row looks busy and is usually marked wrong.
3. Stop where you are told. If the question says "until the program ends" or "for three iterations", stop there. Add the END row only if the program reaches it.

Two instructions change nothing in a trace table except the compare result:

• "CMP / CMI set the comparison result to True or False;"
• "JMP always jumps, JPE jumps on True, JPN jumps on False."

So a row for a jump often has an empty change cell — and that is the correct answer.