Printing and Variables

C++ programs are built from #include directives, a main() function, and statements inside it -- every statement ends with a semicolon.

Your first program

#include <iostream>
using namespace std;

int main() {
    cout << "Hello, world!" << endl;
    return 0;
}

Variables

Every variable's type must be declared before it's used:

#include <string>

int age;
double gpa;
string name;

Assigning values

int age = 20;
double gpa = 4.5;
string name = "Ada";

= is the assignment operator here -- == is only for comparisons.

Getting input

#include <iostream>
using namespace std;

int main() {
    string name;
    cout << "What is your name? ";
    cin >> name;
    cout << "Hello, " << name << endl;
    return 0;
}

Comments

// This is a comment -- C++ ignores everything after //
/* This is a
   multi-line comment */

Why This Matters for Your Exams

C++ is strongly, statically typed -- unlike Python, every variable's type is fixed the moment it's declared and checked before the program even compiles. Forgetting a semicolon or mismatching a type is the single most common beginner compile error.

Try it yourself

Change the name below and press Run to see C++'s own output.