Copy Array Elements in C: Program to Copy One Array to Another

Introduction

In this tutorial, we will learn how to write a C program to copy elements from one array to another.

Copying an array is a common operation in programming. It is used in many real-world applications, such as:

• Creating a backup copy of data before modification
• Passing data to functions without modifying the original
• Sorting or processing data while keeping the original intact
• Duplicating data for parallel processing

C Program to Copy Array Elements (Method 1: Using Loop)

#include <stdio.h>

int main() {
    int n, i;
    
    // Ask user for number of elements
    printf("Enter the number of elements: ");
    scanf("%d", &n);
    
    // Declare arrays
    int source[n];
    int destination[n];
    
    // Read elements into the source array
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &source[i]);
    }
    
    // Copy elements from source to destination
    for(i = 0; i < n; i++) {
        destination[i] = source[i];
    }
    
    // Display source array
    printf("\nSource array: ");
    for(i = 0; i < n; i++) {
        printf("%d ", source[i]);
    }
    
    // Display destination array
    printf("\nDestination array: ");
    for(i = 0; i < n; i++) {
        printf("%d ", destination[i]);
    }
    printf("\n");
    
    return 0;
}

Sample Output

Enter the number of elements: 5
Enter 5 elements:
10 20 30 40 50

Source array: 10 20 30 40 50
Destination array: 10 20 30 40 50

Another Example:

Enter the number of elements: 4
Enter 4 elements:
5 15 25 35

Source array: 5 15 25 35
Destination array: 5 15 25 35

Program Explanation

Let's break down the code step by step:

1. Include Header File: #include <stdio.h> includes the standard input/output library.
2. Declare Variables:
   • int n; — stores the number of elements
   • int i; — loop counter
3. Declare Arrays:
   • int source[n]; — the original array
   • int destination[n]; — the array where elements will be copied
4. Get User Input: Prompts the user to enter the number of elements and then reads them into the source array.
5. Copy the Array: The for loop copies each element from source to destination:
   • destination[i] = source[i];
   • This copies the value at index i from source to index i in destination
6. Display Results: Prints both the source and destination arrays to verify the copy.
7. Return: return 0; indicates successful program execution.

Method 2: Using memcpy Function (More Efficient)

The memcpy() function from string.h library provides a faster way to copy arrays. It copies a block of memory from source to destination.

#include <stdio.h>
#include <string.h>  // Required for memcpy

int main() {
    int n, i;
    
    printf("Enter the number of elements: ");
    scanf("%d", &n);
    
    int source[n];
    int destination[n];
    
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &source[i]);
    }
    
    // Copy using memcpy
    memcpy(destination, source, n * sizeof(int));
    
    // Display source array
    printf("\nSource array: ");
    for(i = 0; i < n; i++) {
        printf("%d ", source[i]);
    }
    
    // Display destination array
    printf("\nDestination array: ");
    for(i = 0; i < n; i++) {
        printf("%d ", destination[i]);
    }
    printf("\n");
    
    return 0;
}

Sample Output:

Enter the number of elements: 6
Enter 6 elements:
10 20 30 40 50 60

Source array: 10 20 30 40 50 60
Destination array: 10 20 30 40 50 60

How memcpy Works

• memcpy(destination, source, n * sizeof(int));
• destination: Pointer to the destination array
• source: Pointer to the source array
• n * sizeof(int): Number of bytes to copy
• Advantage: Faster than manual loop for large arrays

Algorithm to Copy Array Elements

1. Start
2. Read the number of elements (n)
3. Read n elements into the source array
4. For i = 0 to n-1:
   • Set destination[i] = source[i]
5. Print both source and destination arrays
6. End

#include <stdio.h>

int main() {
    int n, i;
    
    printf("Enter the number of elements: ");
    scanf("%d", &n);
    
    int source[n];
    int destination[n];
    
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &source[i]);
    }
    
    // Copy in reverse order
    for(i = 0; i < n; i++) {
        destination[i] = source[n - 1 - i];
    }
    
    printf("\nSource array: ");
    for(i = 0; i < n; i++) {
        printf("%d ", source[i]);
    }
    
    printf("\nDestination (reversed): ");
    for(i = 0; i < n; i++) {
        printf("%d ", destination[i]);
    }
    printf("\n");
    
    return 0;
}

Frequently Asked Questions

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