Conditionals and Loops

Learn how to write programs that make decisions and repeat actions using if-statements, while-loops, and for-loops in C.

Now that you can store data with variables, let’s add logic to your programs with conditionals and loops.

This lesson will teach your programs how to make decisions and do things over and over again — two key skills for any kind of automation or embedded programming.

Conditionals (if-statements)

Use if to check if something is true, and act accordingly.

#include <stdio.h>

int main() {
    int temperature = 30;   // Set the variable temperature to 30

    if (temperature > 25) { // Check if temperature is greater than 25
        printf("It's hot today!\n"); 
    } else {                // If not, do this
        printf("It's not too hot.\n");
    }

    return 0;               // End the program
}

You can also use else if:

if (temp > 25) {
    // ...
} else if (temp > 15) {
    // ...
} else {
    // ...
}

Comparison Operators

Loops

Loops let you repeat something multiple times — great for blinking LEDs, checking sensors, or running forever.

while Loop

int count = 0;

while (count < 5) { // Repeat the code block while count is less than 5
    printf("Count: %d\n", count);
    count++; // Increment count by 1
}

This will print Count: 0 through Count: 4.

for Loop

A for loop is a shorter way to repeat something a specific number of times. for loops require three parts:

1. Initialization: Set a starting point: int i = 0; this sets the starting value of the loop variable i.
2. Condition: Check if the loop should continue: i < 5; this checks if i is less than 5, when the value of i reaches 5, the loop stops.
3. Increment: Update the loop variable after each iteration: i++ this increases the value of i by 1 each time the loop runs.

for (int i = 0; i < 5; i++) {
    printf("i = %d\n", i);
}

This does the same thing as the while loop above — it’s just shorter.

Infinite Loop

Microcontrollers often run in an infinite loop, doing tasks over and over:

while (1) {
    // Do something forever
}

We’ll use this when we get to controlling the LED!

Summary

You now know how to:

• Make decisions with if, else if, and else
• Repeat actions with while and for loops
• Use loops for continuous behavior — a key part of embedded programming

Next up: Functions in C, where we’ll start breaking our programs into reusable chunks!

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