Recursive function in assembly in ARM Architecture - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a recursive function?

A recursive function is a function that calls itself to solve smaller parts of a problem until it reaches a simple case it can solve directly.

intermediate

How does a recursive function manage multiple calls in assembly?

It uses the stack to save return addresses and local data for each call, so it can return correctly after each recursive step.

beginner

Why is the base case important in a recursive function?

The base case stops the recursion by providing a simple answer, preventing infinite calls and eventual program crash.

beginner

In ARM assembly, which register typically holds the return address for a function call?

The link register (LR) holds the return address when a function is called using the BL (branch with link) instruction.

intermediate

What is the role of the stack pointer (SP) in recursive functions in ARM assembly?

The stack pointer (SP) tracks the top of the stack, where return addresses and local variables are saved for each recursive call.

What does a recursive function do?

A Runs only once

B Calls only other functions

C Calls itself to solve smaller problems

D Never stops running

A recursive function calls itself to break down a problem into smaller parts.

Which ARM register stores the return address after a function call?

A R0

B SP

C PC

D LR

The LR (link register) holds the return address after a BL instruction.

Why is the base case necessary in recursion?

A To start the recursion

B To stop infinite calls

C To call other functions

D To use more memory

The base case stops recursion to prevent infinite loops.

What does the stack pointer (SP) do during recursion?

A Tracks the top of the stack for saved data

B Stores the current instruction

C Holds function arguments only

D Points to the program start

SP points to the top of the stack where return addresses and local data are saved.

How does ARM assembly save the return address before a recursive call?

A By storing LR on the stack

B By using R0 register

C By jumping directly to main

D By clearing the stack

Before a recursive call, LR is saved on the stack to preserve the return address.

Explain how a recursive function works in ARM assembly, including how it uses the stack and registers.

Think about how the function calls itself and what needs to be saved each time.

Describe the importance of the base case in a recursive function and what could happen if it is missing.

Consider what stops the function from calling itself forever.