Return value in R0 in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to move the return value 5 into register R0.

ARM Architecture

MOV R0, [1]

Drag options to blanks, or click blank then click option'

A#5

BR1

C5

DR0

Attempts:

3 left

💡 Hint

Common Mistakes

Using MOV R0, 5 without the '#' causes an error.

Using MOV R0, R1 moves the value from R1, not the number 5.

In ARM assembly, immediate values are prefixed with '#'. So to move the value 5 into R0, use MOV R0, #5.

2fill in blank

medium

Complete the code to return the value stored in register R2 by moving it into R0.

ARM Architecture

MOV [1], R2

Drag options to blanks, or click blank then click option'

AR0

BR1

CR3

DR2

Attempts:

3 left

💡 Hint

Common Mistakes

Moving R2 into R1 does not return the value.

Moving R2 into itself does not change the return register.

The ARM calling convention uses R0 to hold return values. To return the value in R2, move it into R0 with MOV R0, R2.

3fill in blank

hard

Fix the error in the code to correctly return the value 10 in R0.

ARM Architecture

MOV R0, [1]

Drag options to blanks, or click blank then click option'

A10

B#10

CR10

DR1

Attempts:

3 left

💡 Hint

Common Mistakes

Writing MOV R0, 10 without '#' causes an error.

Using MOV R0, R10 moves from register R10, not the number 10.

Immediate values must be prefixed with '#'. So to move 10 into R0, write MOV R0, #10.

4fill in blank

hard

Fill both blanks to move the value from R3 into R0 and then branch to the function return.

ARM Architecture

MOV [1], R3
B [2]

Drag options to blanks, or click blank then click option'

AR0

BLR

CR1

DPC

Attempts:

3 left

💡 Hint

Common Mistakes

Branching to PC causes an infinite loop.

Moving value into R1 does not set the return value.

To return a value, move it into R0. Then branch to the address in LR (link register) to return from the function.

5fill in blank

hard

Fill all three blanks to load immediate 7 into R4, move it to R0 for return, and branch back to the caller.

ARM Architecture

MOV [1], [2]
MOV [3], R4
B LR

Drag options to blanks, or click blank then click option'

AR4

B#7

CR0

DR7

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting '#' before 7.

Moving value into wrong register before return.

First, load immediate 7 into R4 with MOV R4, #7. Then move R4 into R0 to set the return value. Finally, branch to LR to return.