In the world of programming, the need of swapping variables is a common occurrence. Whether you’re working on a simple task or a more complex problem, knowing how to exchange the values of two variables can be extremely useful. In this blog post, we will explore a basic C program that demonstrates how to swap two variables using three different methods. This fundamental concept is not only essential for beginners but also serves as a building block for more advanced programming tasks.

Method 1: Understanding Swapping Variables Using a Temporary Third Variable:

Before we dive into the code, let’s understand the concept of variable swapping. Swapping variables means interchanging their values. In this case, we will use a temporary variable to store one variable’s value temporarily while we exchange the values of the two variables.

The C Code:

Here’s the C code that accomplishes variable swapping:

#include <stdio.h>

int main() {
    int p, q, c;
    printf("Enter values of p and q: ");
    scanf("%d %d", &p, &q);

    printf("Before swapping, p = %d and q = %d\n", p, q);

    c = p;
    p = q;
    q = c;

    printf("Values after swapping, p = %d and q = %d\n", p, q);

    return 0;
}

Explanation of the Code:

1. We start by including the standard I/O library, <stdio.h> which provides functions for input and output operations.
2. Inside the main function, we declare three integer variables: p, q, and c. p and q are the variables we want to swap, and c is a temporary variable used for swapping.
3. We prompt the user to input values for p and q using scanf. The scanf function reads two integer values separated by a space and stores them in p andqb.
4. We print the values of p and q before swapping using printf.
5. To swap p and q, we use the temporary variable c. First, we store the value of p in c, effectively preserving it. Then, we assign the value of q to p and, finally, assign the value stored in c (the original value of p) to q.
6. We print the values of p and q after swapping to demonstrate that the swap has occurred.

Output :

#include <stdio.h>

int main() {
    int p, q;
    printf("Enter values of p and q: ");
    scanf("%d %d", &p, &q);

    printf("Values before swapping: p = %d and q = %d\n", p , q);

    p = p ^ q;
    q = p ^ q;
    p = p ^ q;

    printf("After swapping: p = %d and q = %d\n", p, q);

    return 0;
}

#include <stdio.h>

int main() {
    int p, q;
    printf("Enter values of p and q: ");
    scanf("%d %d", &p, &q);

    printf("Before swapping: p = %d and q = %d\n", p, q);

    p = p + q;
    q = p - q;
    p = p - q;

    printf("After swapping: p = %d and q = %d\n", p, q);

    return 0;
}

Explanation of the Code:

1. We include the standard I/O library, <stdio.h>, to handle input and output operations.
2. Inside the main function, we declare two integer variables, p and q, which we want to swap.
3. We prompt the user to input values for p and q using scanf.
4. To visualize the initial values, we print the values of p and q before swapping.
5. The actual swapping is achieved through arithmetic operations. Here’s how it works:
   • p = p + q adds the values of p and q and stores the result in p, effectively combining both values.
   • q = p - q subtracts the new value of q from p, which results in the original value of p. This step assigns the original value of p to q.
   • Finally, p = p - q subtracts the value of the newly swapped q from p, resulting in the original value of b being assigned to p.
6. After swapping, we print the values of p and q to confirm that the exchange has taken place successfully.

Output:

Enter values of p and q: 50
90
Values before swapping p = 50 and q = 90
After swapping p = 90 and q = 50

Clearer Explanation of Output:

• Initialize p and q:
  • p = 90
  • q = 50
• First step: p = p + q:
  • p becomes 90 + 50, which is 140.
  • So, p is now 140.
• Second step: q = p - q:
  • q becomes 140 - 50, which is 90.
  • So, q is now 90.
• Third step: p = p - q:
  • p becomes 140 - 90, which is 50.
  • Now, p holds the original value of q, which is 50.

Conclusion

Swapping variables, whether using a temporary variable, bitwise XOR, or arithmetic operations, is a fundamental programming concept that serves various purposes. Here’s a conclusion summarizing the key points of swapping variables:

1. Traditional Swapping with a Temporary Variable:
   • This method involves using a temporary variable to hold one of the values temporarily while you exchange the values of two variables.
   • It is simple, easy to understand, and commonly used in programming.
   • Suitable for most situations and doesn’t rely on specific properties of the data types involved.
2. Bitwise XOR Swapping:
   • XOR-based swapping is a clever technique that leverages the properties of the XOR operation.
   • It efficiently exchanges the values of two variables without using a temporary variable.
   • XOR swapping is memory-efficient and can be particularly useful in situations where memory allocation is constrained.
3. Arithmetic Swapping:
   • Arithmetic-based swapping relies on addition and subtraction operations.
   • It is another memory-efficient method to swap variables without a temporary variable.
   • Simple and straightforward, it can be a valuable tool when memory efficiency is a concern.

In conclusion, swapping variables is a fundamental skill in programming, and the method you choose depends on your specific needs and constraints. Traditional swapping with a temporary variable is often the easiest to understand and implement, while bitwise XOR and arithmetic swapping offer memory-efficient alternatives. Understanding these different methods equips you with valuable tools for solving a wide range of programming challenges efficiently and elegantly.

Read this also: Clarity to 2 Concepts- Post-Decrement and Pre-Decrement in C (codershot.com)

Here’s the YouTube video for more convenience