C++ Course

Cheatsheet

A quick reference — the essential syntax of modern C++ on a single page. Press Ctrl/Cmd + P to print it.

Variables and basic types

Declarations

int x = 42;             // Integer
double pi = 3.14159;    // Floating point
char grade = 'A';       // Single character (single quotes)
bool isFun = true;      // Boolean (true/false)
const int Max = 100;    // Constant
auto inferred = 5.5;    // Automatic type deduction

Every statement in C++ must end with a semicolon (;).

Standard strings

#include <string>

std::string name = "Alice";
std::string greet = "Hello " + name;
int len = greet.length();  // or greet.size()

Always use double quotes for strings and include <string>.

Control Flow

Conditionals (if / else)

if (score >= 90) {
    std::cout << "Excellent!";
} else if (score >= 60) {
    std::cout << "Passed";
} else {
    std::cout << "Failed";
}

Loops (for / while)

// Classic for loop
for (int i = 0; i < 5; ++i) {
    std::cout << i << " ";
}

// While loop
while (count > 0) {
    count--;
}

Switch statement

switch (op) {
    case '+':
        res = a + b;
        break;
    case '-':
        res = a - b;
        break;
    default:
        res = 0;
}

Do not forget the break; statement, otherwise execution falls through to next cases.

Functions and References

Basic definition

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

void greet() {
    std::cout << "Hello!";
}

void functions do not return any value.

Pass by Reference (&)

// Modifies the original variable directly
void doubleIt(int& n) {
    n = n * 2;
}

// Pass by const reference (efficient, read-only)
void showName(const std::string& s) {
    std::cout << s;
}

Use const references to pass large objects and avoid expensive copying.

Classes and OOP

Class declaration

class Rectangle {
private:
    int width;
    int height;

public:
    // Constructor
    Rectangle(int w, int h) : width(w), height(h) {}

    int getArea() {
        return width * height;
    }
};

Note the mandatory semicolon (;) after the closing brace of the class.

Object usage

Rectangle rect(5, 4);       // Instantiation
int area = rect.getArea();  // Method call: 20

Input / Output Stream

<iostream> library

#include <iostream>

// Writing to console
std::cout << "Value: " << x << std::endl;

// Reading from console
std::cin >> x;

// boolalpha to print true/false instead of 1/0
std::cout << std::boolalpha << true;

std::endl inserts a new line and flushes the output buffer.

C++ · Cheatsheet — eLearner.app

Variables and basic types

Control Flow

Functions and References

Classes and OOP

Input / Output Stream