If-else implementation in assembly in ARM Architecture - Mini Project: Build & Apply

If-else Implementation in Assembly

📖 Scenario: You are learning how to write simple decision-making code using ARM assembly language. This is useful when you want your program to choose between two actions based on a condition, like checking if a number is positive or negative.

🎯 Goal: Build a small ARM assembly program that uses an if-else structure to check if a number is zero or not, and sets a register to different values accordingly.

📋 What You'll Learn

Create a register with a specific value to test

Set up a label for branching

Use a conditional branch instruction to implement if-else logic

Set a register to one value if the condition is true, another if false

💡 Why This Matters

🌍 Real World

Assembly language is used in low-level programming for embedded systems, device drivers, and performance-critical code where direct control of hardware is needed.

💼 Career

Understanding if-else in assembly helps in debugging, optimizing code, and working with hardware-level programming in fields like embedded systems engineering and systems programming.

1

DATA SETUP: Initialize register with test value

Load the value 5 into register r0 to use as the test number.

ARM Architecture

# Load the value 5 into r0
# Your code here

Need a hint?

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

2

CONFIGURATION: Prepare a label for branching

Create a label called else_part that will mark where the else code starts.

ARM Architecture

MOV r0, #5
# Your code here

Need a hint?

Labels end with a colon : and mark a place in the code.

3

CORE LOGIC: Implement if-else using conditional branch

Compare r0 with zero using CMP r0, #0. Then use the conditional branch BEQ else_part to jump to else_part if r0 is zero. If not zero, set r1 to 1. Then use B end_part to skip over the else part.

ARM Architecture

MOV r0, #5
# Your code here
else_part:

Need a hint?

Use CMP to compare, BEQ to branch if equal, MOV to set r1, and B end_part to skip the else.

4

COMPLETION: Complete else part to set r1 to zero

At label else_part, set r1 to 0. Then create a label end_part: to complete the if-else structure.

ARM Architecture

MOV r0, #5
CMP r0, #0
BEQ else_part
MOV r1, #1
B end_part
else_part:
# Your code here

Need a hint?

After the label else_part, use MOV r1, #0 then add end_part:.