All C++ NOTES

 

Comprehensive C++ Notes

---

1. Introduction to C++

• C++ is a general-purpose programming language created by Bjarne Stroustrup in 1979 as an extension of C.

• It supports procedural, object-oriented, and generic programming paradigms.

• Commonly used for system/software development, game programming, embedded systems, and more.

---

2. Basic Syntax

cpp
#include <iostream>
using namespace std;

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

• #include <iostream>: Includes input/output stream library.

• using namespace std;: Avoids prefixing std:: before cout, cin, etc.

• int main(): Entry point of C++ program.

• cout: Standard output stream.

• endl: End line (newline) character.

---

3. Data Types

Type	Description	Size (typical)
int	Integer	4 bytes
float	Floating point number	4 bytes
double	Double precision float	8 bytes
char	Single character	1 byte
bool	Boolean (true or false)	1 byte
void	Represents no value	N/A

---

4. Variables and Constants

cpp
int age = 25;           // variable
const float PI = 3.14159;  // constant (cannot be changed)

• Variables hold data, constants are fixed values.

• Use const keyword for constants.

---

5. Operators

• Arithmetic: +, -, *, /, %

• Assignment: =, +=, -=, *=, /=

• Comparison: ==, !=, >, <, >=, <=

• Logical: && (AND), || (OR), ! (NOT)

• Increment/Decrement: ++, --

---

6. Control Structures

6.1 Conditional Statements

cpp
if (condition) {
    // code if true
} else if (another_condition) {
    // code if another_condition true
} else {
    // code if all false
}

6.2 Switch Statement

cpp
switch (variable) {
    case 1:
        // code
        break;
    case 2:
        // code
        break;
    default:
        // code
}

6.3 Loops

• For loop:

cpp
for (int i = 0; i < 10; i++) {
    cout << i << endl;
}

• While loop:

cpp
int i = 0;
while (i < 10) {
    cout << i << endl;
    i++;
}

• Do-while loop:

cpp
int i = 0;
do {
    cout << i << endl;
    i++;
} while (i < 10);

---

7. Functions

cpp
int add(int a, int b) {
    return a + b;
}

int main() {
    int sum = add(5, 3);
    cout << sum;
}

• Functions encapsulate reusable code.

• Can have return types, parameters, and default values.

---

8. Arrays and Strings

8.1 Arrays

cpp
int numbers[5] = {1, 2, 3, 4, 5};
cout << numbers[0];  // Output: 1

• Fixed size, stores multiple elements of same type.

8.2 Strings

• Using C-style:

cpp
char name[] = "Alice";

• Using C++ string class:

cpp
#include <string>
string name = "Alice";
cout << name.length();

---

9. Pointers

cpp
int var = 10;
int *ptr = &var;

cout << *ptr;  // Output: 10 (value pointed to)

• Pointer stores memory address.

• Use & to get address, * to dereference.

---

10. References

cpp
int a = 5;
int &ref = a;
ref = 10;   // a is now 10

• Reference is an alias for a variable.

• Must be initialized when declared.

---

11. Structures (struct)

cpp
struct Person {
    string name;
    int age;
};

Person p1;
p1.name = "John";
p1.age = 30;

• Group related variables under one name.

---

12. Object-Oriented Programming (OOP)

12.1 Classes and Objects

cpp
class Car {
public:
    string brand;
    int year;

    void honk() {
        cout << "Beep beep!" << endl;
    }
};

int main() {
    Car myCar;
    myCar.brand = "Toyota";
    myCar.year = 2020;
    myCar.honk();
}

• Class: blueprint for objects.

• Object: instance of a class.

12.2 Access Modifiers

Modifier	Access Level
public	Accessible anywhere
private	Accessible only inside the class
protected	Accessible in class and subclasses

12.3 Constructor and Destructor

cpp
class Car {
public:
    Car() { cout << "Car created\n"; }
    ~Car() { cout << "Car destroyed\n"; }
};

12.4 Inheritance

cpp
class Vehicle {
public:
    void move() { cout << "Moving\n"; }
};

class Car : public Vehicle {
public:
    void honk() { cout << "Honk honk\n"; }
};

---

13. Templates (Generic Programming)

cpp
template <typename T>
T add(T a, T b) {
    return a + b;
}

• Allows functions/classes to work with any data type.

---

14. Exception Handling

cpp
try {
    int x = 5 / 0;
} catch (exception &e) {
    cout << "Error: " << e.what();
}

• Use try, catch, and throw for error handling.

---

15. Standard Template Library (STL)

• Containers: vector, list, map, set, etc.

• Algorithms: sort, search, etc.

• Iterators: used to traverse containers.

Example with vector:

cpp
#include <vector>
#include <algorithm>

vector<int> nums = {5, 3, 9, 1};
sort(nums.begin(), nums.end());

---

16. Input and Output

• Input: cin

• Output: cout

Example:

cpp
int age;
cout << "Enter your age: ";
cin >> age;
cout << "Your age is " << age << endl;

---

17. File I/O

cpp
#include <fstream>

ofstream outfile("file.txt");
outfile << "Hello File";
outfile.close();

ifstream infile("file.txt");
string content;
getline(infile, content);
infile.close();
cout << content;

---

18. Useful Keywords

Keyword	Purpose
static	Shared variable/function, persists
const	Constant value
volatile	Variable can be changed unexpectedly
mutable	Allows modification in const object
friend	Access private members
namespace	Organizes code into logical groups

---

19. Common Best Practices

• Use meaningful variable names

• Keep functions small and focused

• Comment your code for clarity

• Avoid using using namespace std; in headers

• Use nullptr instead of NULL

• Prefer std::vector over raw arrays for safety