1. Structure of a C++ Program
#include <iostream> // Header for input/output
using namespace std;
int main() {
cout << "Hello, World!" << endl; // Print to console
return 0;
}
2. Basic Syntax and Data Types
Variables and Data Types
int age = 25; // Integer
float height = 5.9; // Floating point
double pi = 3.14159; // Double precision float
char grade = 'A'; // Character
bool isStudent = true; // Boolean (true/false)
string name = "Alice"; // String (requires <string> header)
Constants
const double GRAVITY = 9.8; // Unchangeable variable
3. Input/Output (I/O)
#include <iostream>
int main() {
string name;
cout << "Enter your name: ";
cin >> name; // Input
cout << "Hello, " << name << endl; // Output
return 0;
}
4. Operators
int a = 10, b = 3;
int sum = a + b; // Addition
int diff = a - b; // Subtraction
int prod = a * b; // Multiplication
float div = a / (float)b; // Division (type casting)
int mod = a % b; // Modulus
a++; // Increment
b--; // Decrement
5. Conditional Statements
int age = 20;
if (age >= 18) {
cout << "Adult" << endl;
} else {
cout << "Minor" << endl;
}
Else If Example
int score = 85;
if (score >= 90) {
cout << "Grade A" << endl;
} else if (score >= 75) {
cout << "Grade B" << endl;
} else {
cout << "Grade C" << endl;
}
6. Loops
For Loop
for (int i = 1; i <= 5; i++) {
cout << i << endl;
}
While Loop
int count = 1;
while (count <= 5) {
cout << count << endl;
count++;
}
Do-While Loop
int n = 1;
do {
cout << n << endl;
n++;
} while (n <= 5);
7. Functions
#include <iostream>
int add(int a, int b) {
return a + b;
}
int main() {
cout << "Sum: " << add(10, 5) << endl;
return 0;
}
Function with Default Parameters
int power(int base, int exponent = 2) {
return pow(base, exponent);
}
8. Arrays
int numbers[5] = {1, 2, 3, 4, 5};
for (int i = 0; i < 5; i++) {
cout << numbers[i] << endl;
}
9. Strings
#include <string>
string greet = "Hello";
greet += ", World!";
cout << greet << endl;
10. Pointers
int value = 42;
int* ptr = &value; // Pointer to value
cout << "Address: " << ptr << endl; // Print address
cout << "Value: " << *ptr << endl; // Dereference pointer
11. Classes and Objects
class Dog {
public:
string name;
void bark() {
cout << name << " says Woof!" << endl;
}
};
int main() {
Dog myDog;
myDog.name = "Buddy";
myDog.bark();
return 0;
}
12. Constructors
class Car {
public:
string brand;
// Constructor
Car(string b) {
brand = b;
}
};
int main() {
Car car1("Toyota");
cout << "Brand: " << car1.brand << endl;
return 0;
}
13. Inheritance
class Animal {
public:
void eat() {
cout << "This animal eats food." << endl;
}
};
class Cat : public Animal {
public:
void meow() {
cout << "Cat says Meow!" << endl;
}
};
int main() {
Cat kitty;
kitty.eat();
kitty.meow();
return 0;
}
14. Exception Handling
try {
int x = 10 / 0;
} catch (...) {
cout << "Error: Division by zero" << endl;
}
15. File I/O
Writing to a File
#include <fstream>
ofstream file("example.txt");
file << "Hello, File!";
file.close();
Reading from a File
#include <fstream>
ifstream file("example.txt");
string line;
while (getline(file, line)) {
cout << line << endl;
}
file.close();
16. Useful STL (Standard Template Library) Containers
Vectors (Dynamic Arrays)
#include <vector>
vector<int> nums = {1, 2, 3};
nums.push_back(4);
for (int n : nums) {
cout << n << endl;
}
Maps (Key-Value Pairs)
#include <map>
map<string, int> scores;
scores["Alice"] = 90;
scores["Bob"] = 85;
for (auto it : scores) {
cout << it.first << ": " << it.second << endl;
}
This cheat sheet covers the basics of C++ to get you started.