Derived Data Types in C++

Data types are means to identify the type of data and associated operations of handling it. There are three types of data types:

1. Pre-defined Data Types
2. Derived Data Types
3. User-defined Data Types

In this article, the Derived Data Type is explained:

Derived Data Types in C++

The data types that are derived from the primitive or built-in datatypes are referred to as Derived Data Types. These can be of four types namely:

• Function
• Array
• Pointers
• References

Let’s briefly understand each of the following derived datatypes:

1. Function

A Function is a block of code or program segment that is defined to perform a specific well-defined task. A function is generally defined to save the user from writing the same lines of code again and again for the same input. All the lines of code are put together inside a single function and this can be called anywhere required. main() is a default function that is defined in every program of C++.

Syntax

FunctionType FunctionName(parameters)

Example:

The below example demonstrates the use of function in C++.

CPP

// C++ program to demonstrate
// Function Derived Type

#include <iostream>
using namespace std;

// max here is a function derived type
int max(int x, int y)
{
    if (x > y)
        return x;
    else
        return y;
}

// main is the default function derived type
int main()
{
    int a = 10, b = 20;

    // Calling above function to
    // find max of 'a' and 'b'
    int m = max(a, b);

    cout << "m is " << m;
    return 0;
}

Output

m is 20

Explanation: This above program demonstrates the use of function derived types It defines a function called ‘max’ this function returns the maximum of two integers provided as input. In the main function, max function is called to find the maximum of variables ‘a’ and ‘b’ and store it in m and finally print m(max number).

2. Array

An Array is a collection of items stored at continuous memory locations. The idea of array is to represent many instances in one variable.

Syntax

DataType ArrayName[size_of_array];

Example:

The below example demonstrates the use of array in C++.

CPP

// C++ program to demonstrate
// Array Derived Type

#include <iostream>
using namespace std;
int main()
{

    // Array Derived Type
    int arr[5];
    arr[0] = 5;
    arr[2] = -10;

    // this is same as arr[1] = 2
    arr[3 / 2] = 2;

    arr[3] = arr[0];

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

    return 0;
}

Output

5 2 -10 5

Explanation: This above program shows the use of array-derived type. It creates an integer array ‘arr’ and assigns values using indices. Then it prints all the array elements.

3. Pointers

Pointers are symbolic representation of addresses. They enable programs to simulate call-by-reference as well as to create and manipulate dynamic data structures. It’s general declaration in C/C++ has the format:

Syntax

datatype *var_name;

for example: int *ptr; (ptr points to an addresswhich holds int data).

Example:

The below example demonstrates the use of class in C++.

CPP

// C++ program to illustrate
// Pointers Derived Type
#include <iostream>
using namespace std;

void geeks()
{
    int var = 20;

    // Pointers Derived Type
    // declare pointer variable
    int* ptr;

    // note that data type of ptr
    // and var must be same
    ptr = &var;

    // assign the address of a variable
    // to a pointer
    cout << "Value at ptr = " << ptr << "\n";
    cout << "Value at var = " << var << "\n";
    cout << "Value at *ptr = " << *ptr << "\n";
}

// Driver program
int main() { geeks(); }

Output

Value at ptr = 0x7ffc04f3f894
Value at var = 20
Value at *ptr = 20

Explanation: This above program demonstrates the use of pointers as a derived type. It deca pointer variable ‘ptr’ and assigning the address of a variable ‘var’ to it. It then prints the values of the pointer, the variable, and the dereferenced pointer, showcasing the basics of pointer usage in C++.

4. Reference

When a variable is declared as reference, it becomes an alternative name for an existing variable. A variable can be declared as reference by putting ‘&’ in the declaration.

Syntax

data_type &ref = variable;

Example:

The below example demonstrates the use of reference in C++.

CPP

// C++ program to illustrate
// Reference Derived Type

#include <iostream>
using namespace std;

int main()
{
    int x = 10;

    // Reference Derived Type
    // ref is a reference to x.
    int& ref = x;

    // Value of x is now changed to 20
    ref = 20;
    cout << "x = " << x << endl;

    // Value of x is now changed to 30
    x = 30;
    cout << "ref = " << ref << endl;

    return 0;
}

Output

x = 20
ref = 30

Explanation: The above program demonstrates the use of reference-derived type. A reference ‘ref’ to an integer variable ‘x. is created’. If the value of ‘ref’ is changed the value ‘x,’ is also modified and vice versa.

Conclusion

Derived data types in C++ are functions, arrays, pointers, and references offer so many useful tools to handle data. Functions let us write the reusable code. Arrays help manage multiple items and data very efficiently. Pointers allows the flexible memory use and also referencing. References provide a way to create alias and simpler ways to work with variables. Overall, these derived datatypes make C++ coding more systematic and effective.