Conditional branch with flags in ARM Architecture - Mini Project: Build & Apply

Conditional Branch with Flags in ARM Assembly

📖 Scenario: You are programming a simple ARM assembly routine that checks a number and decides what to do based on whether the number is zero or not.This is like checking if a light switch is off or on and then acting accordingly.

🎯 Goal: Build a small ARM assembly program that uses conditional branch instructions based on flags to decide if a number is zero or not.

📋 What You'll Learn

Create a register with a specific number

Set up a comparison instruction to update flags

Use a conditional branch instruction that checks the zero flag

Add a label to branch to when the condition is met

💡 Why This Matters

🌍 Real World

Conditional branches with flags are used in ARM assembly to make decisions, like checking if a value is zero before continuing.

💼 Career

Understanding conditional branches is essential for embedded systems programming, firmware development, and low-level software engineering.

1

Set up the number in a register

Write ARM assembly code to load the number 5 into register r0.

ARM Architecture

# Load the number 5 into r0
# Your code here

Need a hint?

Use the MOV instruction to put the number 5 into r0.

2

Compare the number with zero

Add ARM assembly code to compare the value in r0 with zero using the CMP instruction.

ARM Architecture

MOV r0, #5
# Compare r0 with zero
# Your code here

Need a hint?

The CMP instruction sets flags based on the subtraction of the second operand from the first.

3

Add a conditional branch based on zero flag

Write ARM assembly code to branch to label is_zero if the zero flag is set, using the BEQ instruction.

ARM Architecture

MOV r0, #5
CMP r0, #0
# Branch to is_zero if zero flag is set
# Your code here

Need a hint?

The BEQ instruction branches if the zero flag is set, meaning the compared values were equal.

4

Add the label for the branch target

Add the label is_zero below the branch instruction to mark the location where the program jumps if the number is zero.

ARM Architecture

MOV r0, #5
CMP r0, #0
BEQ is_zero
# Add the label is_zero here
# Your code here

Need a hint?

A label is written as a name followed by a colon :.