An Array Reversal Program in C is a common task that involves reversing the order of elements in an array. This task helps in understanding array manipulation, looping structures, and basic input/output in C.

Example: Array Reversal Program

In this example, we will write a program that allows the user to input a specific number of integers into an array and then reverses the order of those integers.

C Program to Reverse an Array

#include <stdio.h>

int main() {
    int n, i;
    int arr[100]; // Declare an array of size 100

    // Input the number of elements in the array
    printf("Enter the number of elements in the array: ");
    scanf("%d", &n);

    // Input elements into the array
    printf("Enter %d integers:\n", n);
    for (i = 0; i < n; i++) {
        printf("Element %d: ", i + 1);
        scanf("%d", &arr[i]); // Store each element in the array
    }

    // Reverse the array
    int start = 0;               // Starting index
    int end = n - 1;            // Ending index
    int temp;                   // Temporary variable for swapping

    while (start < end) {
        // Swap the elements at the start and end indices
        temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;

        // Move the indices towards the center
        start++;
        end--;
    }

    // Output the reversed array
    printf("The reversed array is:\n");
    for (i = 0; i < n; i++) {
        printf("%d ", arr[i]); // Print each element
    }
    printf("\n");

    return 0;
}

Explanation:

1. Variable Declarations:

   • int n: This variable holds the number of elements the user wants to input.
   • int i: Loop counter for iterating through the array.
   • int arr[100]: Declares an integer array of size 100 to store the elements.

2. Input for Array Size:

   • The program prompts the user to enter the number of elements they want to reverse and stores this value in n.

3. Input for Array Elements:

   • A for loop is used to iterate from 0 to n-1, prompting the user to input each integer, which is stored in the array arr.

4. Reversing the Array:

   • Two indices, start and end, are initialized to point to the first and last elements of the array, respectively.
   • A while loop continues to execute as long as start is less than end.
   • Inside the loop:
     • The elements at start and end are swapped using a temporary variable temp.
     • The start index is incremented, and the end index is decremented to move toward the center of the array.

5. Output the Reversed Array:

   • Finally, a for loop iterates over the array to print the elements in their new reversed order.

Sample Output:

Example 1:

Enter the number of elements in the array: 5
Enter 5 integers:
Element 1: 10
Element 2: 20
Element 3: 30
Element 4: 40
Element 5: 50
The reversed array is:
50 40 30 20 10

Example 2:

Enter the number of elements in the array: 3
Enter 3 integers:
Element 1: 5
Element 2: 15
Element 3: 25
The reversed array is:
25 15 5

Key Points:

• Array Manipulation: The program demonstrates how to manipulate arrays through indexing and swapping.
• Looping: The use of both for and while loops illustrates different ways to traverse an array.
• Input/Output: Standard input/output functions are used for user interaction.

Variations:

You can modify the program to:

• Handle larger arrays dynamically using dynamic memory allocation (with malloc).
• Reverse only a portion of the array based on user input.
• Implement a function for array reversal to modularize the code.

This program serves as a foundational exercise for understanding array manipulation and control structures in C programming.