PyQdeck LogoPyQdeckSubjectsSyllabusBlog
Back to the 2015 paper

Module 2: x86 Architecture, CPU Control, I/O, Memory System Design

20152m

Briefly explain subroutine call and return.

Search GoogleAsk AI
Worked SolutionAI Assisted

Subroutine Call / Return Mechanism (2 Marks)

Uses stack to save return address and transfer control:

CALL (Call Subroutine):

  1. Push return address: SP ← SP - 1; M[SP] ← PC (PC holds next sequential address after CALL)
  2. Jump to subroutine: PC ← effective address of subroutine (branch target)

Assembly: CALL 2050H does above in one micro-sequence.

RET (Return):

  1. Pop return address: PC ← M[SP]; SP ← SP + 1
  2. Fetch resumes at saved location.

Stack LIFO supports nesting: each CALL pushes new address, each RET pops in reverse order, enabling recursion. Link register variant saves PC in LR instead of memory stack for low-overhead leaf calls.

Similar questions

MICROPROCESSORSDefine subroutine. Explain the execution of subroutine function.20247mMICROPROCESSORSWhat is Subroutine? Explain the execution of Subroutine function.20227mCOMPUTER ORGANIZATION & ARCHITECTUREExplain the use of subroutine with the help of suitable example.20162mMICROPROCESSORSExplain subroutine instructions and stack operations in 8051.20257m
PreviousWhat is the importance of cache memory in a computer?NextWhat do you mean by array processors? How are they different from scalar processors?
Student FinanceWeb Platform

Pocketly — Personal Finance for Students

Keep your hostel and college expenses under control. Track accounts, log spending in seconds, and stay within your monthly budget.

Open Pocketly