Derived data types are complex data types that are built using the basic (primary) data types. They are used to store and manage collections of data or to handle more advanced programming concepts like memory management. The primary derived types in C are Arrays, Pointers, and Functions.

1. Arrays ⛓️

An array is a fixed-size, sequential collection of elements of the same data type. Think of it as a row of numbered containers, where each container holds the same kind of item.

·         Purpose: To store multiple related values under a single variable name.

·         Declaration: data_type array_name[size];

Example

This example stores the marks of 5 subjects in an integer array. Array elements are accessed using an index, which starts from 0.

C

#include <stdio.h>

int main() {

    // Declare and initialize an array of 5 integers

    int marks[5] = {85, 90, 78, 92, 88};

    printf("Displaying marks of subjects:\n");

    // Use a loop to access each element of the array

    // The index goes from 0 to 4

    for (int i = 0; i < 5; i++) {

        // marks[i] accesses the element at the current index

        printf("Subject %d: %d\n", i + 1, marks[i]);

    }

    return 0;

}

2. Pointers 👉

A pointer is a special variable that does not store data directly but instead stores the memory address of another variable. It "points to" the location where the data is stored.

·         Purpose: Pointers are essential for dynamic memory allocation, creating complex data structures (like linked lists), and for allowing functions to modify the original variables passed to them.

·         Declaration: data_type *pointer_name;

o    The asterisk (*) indicates that it's a pointer.

Example

This example shows how a pointer stores the address of a variable and how to access the variable's value through the pointer.

C

#include <stdio.h>

int main() {

    int age = 25; // A normal integer variable

    // A pointer 'ptr' that can store the address of an integer

    int *ptr;

    // The '&' operator gets the memory address of 'age'

    ptr = &age;

    printf("Value of age (direct access): %d\n", age);

    // The '*' operator dereferences the pointer to get the value it points to

    printf("Value of age (via pointer): %d\n", *ptr);

    printf("Memory address of age: %p\n", (void *)ptr);

    return 0;

}

3. Functions ⚙️

A function is a self-contained block of code that performs a specific task. While not a data type in the same way as an array, it's considered derived because its definition involves other data types for its parameters and return value.

·         Purpose: To break down a large program into smaller, reusable, and manageable modules, improving readability and maintainability.

·         Declaration (Prototype): return_type function_name(parameter_type1, parameter_type2);

Example

This example defines a simple function add that takes two integers and returns their sum. The main function calls this add function.

C

#include <stdio.h>

// Function prototype (declaration)

int add(int a, int b);

// The main function - program execution starts here

int main() {

    int num1 = 10;

    int num2 = 20;

    int sum;

    // Calling the 'add' function and storing its return value

    sum = add(num1, num2);

    printf("The sum of %d and %d is: %d\n", num1, num2, sum);

    return 0;

}

// Function definition

int add(int a, int b) {

    // The 'return' keyword sends a value back to the caller

    return a + b;

}