Defining a function

int square(int x) {
    return x * x;
}

int main() {
    cout << square(5) << endl;
    return 0;
}

A function's return type is declared before its name; return sends a value back to the caller. A function declared void returns nothing at all.

Void functions

void greet(string name) {
    cout << "Hello, " << name << "!" << endl;
}

int main() {
    greet("Ada");
    return 0;
}

Arrays

An array is a fixed-size, ordered collection -- its size is part of its declaration:

string fruits[3] = {"apple", "banana", "cherry"};
cout << fruits[0] << endl; // apple -- indexing starts at 0

Looping over an array

for (int i = 0; i < 3; i++) {
    cout << fruits[i] << endl;
}

Why This Matters for Your Exams

Unlike a Python list, a C++ array's size is fixed at declaration, and C++ does nothing to stop you reading or writing past its bounds -- no error, just undefined (and often wrong) behavior. Always declare arrays large enough, and track their length separately instead of guessing.

Try it yourself