Exam-style question
Try this first
Describe what happens to stack frames when subroutine A calls subroutine B, and subroutine B then calls subroutine C. Explain the order in which the frames are used and removed, and why each frame must retain its own information.
Model answer
What a good answer should say
- A stack frame for subroutine A is active first.
- When A calls B, a new frame for B is placed on top of A's frame.
- The B frame contains B's return address, parameters and local variables.
- If B calls C, a new C frame is placed on top of B's frame and contains C's corresponding information.
Explanation
Why this works
The essential sequence is last in, first out: C's frame is removed first, then B's, while A's remains below them. The explanation must also connect separate frames with the preservation of return addresses, parameters and local variables.
Common mistake
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