CIntermediate

C Functions

Write functions in C: define and call functions, return values, recursion, and passing arguments by reference with pointers.

01Define a function

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main.c

#include <stdio.h>

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

int main() {
    printf("%d\n", add(3, 4));
    return 0;
}

Output

02Recursion (factorial)

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main.c

#include <stdio.h>

int factorial(int n) {
    if (n <= 1) return 1;
    return n * factorial(n - 1);
}

int main() {
    printf("%d\n", factorial(5));
    return 0;
}

Output

03Pass by reference

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main.c

#include <stdio.h>

void increment(int *x) {
    (*x)++;
}

int main() {
    int n = 10;
    increment(&n);
    printf("%d\n", n);
    return 0;
}

Output

04Sum with a loop

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main.c

#include <stdio.h>

int sum_to(int n) {
    int total = 0;
    for (int i = 1; i <= n; i++) total += i;
    return total;
}

int main() {
    printf("%d\n", sum_to(10));
    return 0;
}

Output