Data Types

In C++, data types are crucial for defining how data is stored, manipulated, and understood by the compiler. There are three main categories:

• Pre-defined (Primitive) Data Types
• User-defined Data Types
• Derived Data Types

Derived Data Types in C++ are created from pre-existing data types and include:

• Function
• Array
• Pointers
• References

1. Function: A function is a reusable block of code designed to perform a specific task. It prevents code duplication by encapsulating instructions that can be invoked multiple times.

Syntax:

FunctionType FunctionName(parameters);

Example:

#include <iostream>
using namespace std;

int max(int x, int y) {
    return (x > y) ? x : y;
}

int main() {
    int a = 10, b = 20;
    cout << "Max is " << max(a, b);
    return 0;
}

Output:

Max is 20

2. Arrays: An array is a collection of elements stored in contiguous memory locations, all of which are of the same type. Arrays allow multiple data items to be represented with a single variable name.

Syntax:

DataType ArrayName[size_of_array];

Example:

#include <iostream>
using namespace std;

int main() {
    int arr[5];
    arr[0] = 5;
    arr[2] = -10;
    arr[1] = 2;
    arr[3] = arr[0];

    cout << arr[0] << " " << arr[1] << " " << arr[2] << " " << arr[3];
    return 0;
}

Output:

5 2 -10 5

3. Pointers: Pointers hold the memory address of another variable. They are useful for dynamic memory allocation, manipulating data structures, and enabling functions to simulate call-by-reference.

Example:

#include <iostream>
using namespace std;

void displayPointerExample() {
    int var = 20;
    int* ptr = &var;

    cout << "Address stored in ptr = " << ptr << endl;
    cout << "Value of var = " << var << endl;
    cout << "Value pointed by ptr = " << *ptr << endl;
}

int main() {
    displayPointerExample();
    return 0;
}

Output:

Address stored in ptr = 0x7ffc04f3f894
Value of var = 20
Value pointed by ptr = 20

4. References: A reference is an alternative name for an existing variable. References are often used to avoid copying data and enable efficient parameter passing in functions.

#include <iostream>
using namespace std;

int main() {
    int x = 10;
    int& ref = x;

    ref = 20;
    cout << "x = " << x << endl;

    x = 30;
    cout << "ref = " << ref << endl;

    return 0;
}

Output:

x = 20
ref = 30

User-defined data types are types that are created by the programmer, extending the built-in data types. These types include:

• Class
• Structure
• Union
• Enumeration (enum)
• Typedef

1. Class: A Class in C++ serves as the blueprint for creating objects, encapsulating data and functions that operate on the data. It is the foundation of Object-Oriented Programming in C++.

Syntax:

class ClassName {
    // Access specifier
public:
    // Data Members and Member Functions
};

Example:

#include <iostream>
using namespace std;

class Student {
public:
    string name;

    void display() {
        cout << "Student's name: " << name << endl;
    }
};

int main() {
    Student s1;
    s1.name = "Alice";
    s1.display();
    return 0;
}

Output:

Student's name: Alice

2. Structure : A Structure is a collection of variables (possibly of different types) under a single name. It is commonly used to group related data.

Example:

#include <iostream>
using namespace std;

struct Point {
    int x, y;
};

int main() {
    Point p1;
    p1.x = 5;
    p1.y = 10;
    cout << "Point: (" << p1.x << ", " << p1.y << ")" << endl;
    return 0;
}

Output:

Point: (5, 10)

3. Union: A Union is similar to a structure, but all members share the same memory location, meaning it can store only one of its members’ values at any given time.

Example:

#include <iostream>
using namespace std;

union Data {
    int integer;
    char character;
};

int main() {
    Data d;
    d.integer = 65;
    cout << "Integer: " << d.integer << endl;
    d.character = 'B';
    cout << "Character: " << d.character << endl;
    return 0;
}

Output:

Integer: 65
Character: B

4. Enumeration (enum) : An Enumeration is a user-defined type consisting of a set of named integral constants. It helps improve code readability and maintainability by providing meaningful names to numeric values.

Examples:

#include <iostream>
using namespace std;

enum Week { Sun = 1, Mon, Tue, Wed, Thu, Fri, Sat };

int main() {
    Week day = Tue;
    cout << "Day value: " << day << endl;
    return 0;
}

Output:

Day value: 3

5. Typedef : The typedef keyword in C++ allows you to create an alias for existing data types, making the code more readable and maintainable.

Example:

#include <iostream>
using namespace std;

typedef unsigned int UINT;

int main() {
    UINT age = 25;
    cout << "Age: " << age << endl;
    return 0;
}

Output:

Age: 25