C: Functions

#include <stdio.h>

int plus_one(int n) { /* defining the function */
    return n + 1;
}

int main(void){
    int i = 10, j;

    j = plus_one(i); /* calling the function */
    printf("i + 1 is %d\n", j);

    return 0;
}

Adding int before a function simply states that the function returns a datatype of integer; void means it returns nothing.

Define a function before calling/using it, else the compiler won’t know what it is when it runs the main function.