Loop implementation in assembly in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the loop counter register.

ARM Architecture

MOV R0, [1]

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A#10

BR1

C#0

DR2

Attempts:

3 left

💡 Hint

Common Mistakes

Using another register instead of an immediate value to initialize the counter.

Forgetting the '#' symbol before the number.

The instruction MOV R0, #10 sets the register R0 to the immediate value 10, which is commonly used to initialize a loop counter.

2fill in blank

medium

Complete the code to decrement the loop counter register.

ARM Architecture

SUB [1], [1], #1

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AR0

BR3

CR2

DR1

Attempts:

3 left

💡 Hint

Common Mistakes

Using different registers for destination and operand.

Using the wrong register that was not initialized as the counter.

The instruction SUB R0, R0, #1 subtracts 1 from the value in register R0, effectively decrementing the loop counter.

3fill in blank

hard

Fix the error in the loop condition check instruction.

ARM Architecture

CMP [1], #0

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AR1

BR0

C#0

DR2

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing an immediate value to another immediate value.

Using a register that is not the loop counter.

The CMP R0, #0 instruction compares the loop counter in R0 with zero to check if the loop should continue.

4fill in blank

hard

Fill both blanks to create a loop that repeats until the counter reaches zero.

ARM Architecture

BNE [1]
MOV [2], #0

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Aloop_start

BR0

CR1

Dend_loop

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong label name in the branch instruction.

Resetting the wrong register after the loop.

The BNE loop_start instruction branches back to the label loop_start if the zero flag is not set, meaning the counter is not zero yet. The MOV R0, #0 resets the counter register after the loop ends.

5fill in blank

hard

Fill all three blanks to implement a complete loop that counts down from 5 to 1.

ARM Architecture

loop_start:
MOV [1], [2]
SUB [3], [3], #1
CMP [3], #0
BNE loop_start

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AR0

B#5

DR1

Attempts:

3 left

💡 Hint

Common Mistakes

Using different registers inconsistently for the counter.

Not initializing the counter before the loop.

This code sets register R0 to 5, then uses R0 as the loop counter. It decrements R0 by 1 each time, compares it to zero, and loops back if not zero.