C Academy · Lesson

How Recursion Works

Base cases and the call stack.

What Is Recursion?

Recursion is when a function calls itself to solve a problem. Each call works on a smaller piece of the original problem.

In C, any function can call itself, as long as there is a way for the calls to eventually stop.

Every recursive function needs a base case: a condition where it stops calling itself and returns directly.

Without a base case, the function would call itself forever and crash the program.

int countdown(int n) {
    if (n == 0) return 0; /* base case */
    return countdown(n - 1);
}