Code Examples

Short, runnable examples for the basics. Choose a language and open any example in the compiler.

Hello, World!
Every language starts here: print a message to the screen to check that everything works.
```
#include <stdio.h>

int main(void) {
    printf("Hello, World!\n");
    return 0;
}
```
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Variables

Variables store values such as text, whole numbers and decimals so you can reuse them.

#include <stdio.h>

int main(void) {
    char name[] = "Ada";
    int age = 21;
    double height = 1.75;
    printf("%s %d %.2f\n", name, age, height);
    return 0;
}

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Conditions

if / else lets your program choose a path depending on a value.

#include <stdio.h>

int main(void) {
    int age = 18;
    if (age >= 18) {
        printf("Adult\n");
    } else if (age >= 13) {
        printf("Teenager\n");
    } else {
        printf("Child\n");
    }
    return 0;
}

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Loops

Loops repeat a block of code: use for when you know the count and while when you wait for a condition.

#include <stdio.h>

int main(void) {
    for (int i = 1; i <= 5; i++) {
        printf("%d\n", i);
    }
    int n = 3;
    while (n > 0) {
        printf("Countdown %d\n", n--);
    }
    return 0;
}

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Functions

A function packs code into a reusable block that takes inputs and returns a result.

#include <stdio.h>

int add(int a, int b) {
    return a + b;
}

int main(void) {
    printf("%d\n", add(2, 3));
    return 0;
}

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Fibonacci sequence

Each number is the sum of the two before it. A classic exercise that combines variables, loops and arithmetic.

#include <stdio.h>

int main(void) {
    int a = 0, b = 1;
    for (int i = 0; i < 10; i++) {
        printf("%d ", a);
        int next = a + b;
        a = b;
        b = next;
    }
    return 0;
}

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Hello, World!

Variables

Conditions

Loops

Functions

Fibonacci sequence