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 DataTypes
2. Derived Data Types
3. User-defined DataTypes

In this article, the Derived Data Type is explained:

Derived Data Types

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:

   // 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
   

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:

   // 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
   

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;

   Example:

   int *ptr;   
   
   ptr points to an address
   which holds int data

   Example:

   // C++ program to illustrate
   // Pointers Derived Type
   
   #include <bits/stdc++.h>
   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 = 0x7ffc10d7fd5c
   Value at var = 20
   Value at *ptr = 20
   

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.

   Example:

   // 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