Subtraction is a fundamental operation in mathematics and programming alike. In C programming, subtraction of two numbers is a basic task that every beginner should master. This article will walk you through three distinct methods to perform the subtraction of two numbers in C: using simple arithmetic, user-defined functions, and pointer manipulation. Let’s dive into each method to understand how subtraction can be implemented in various ways.

Three ways to write a program for the “Subtraction of two numbers in C”

Method 1) Subtraction of two numbers in C using Simple Arithmetic

The most straightforward way to subtract two numbers in C is by using basic arithmetic operators. Here’s a simple example that demonstrates this approach.

Code Example

#include <stdio.h>

int main() {
    // Declare variables
    int num1, num2, result;

    // Initialize variables
    num1 = 10;
    num2 = 5;

    // Perform subtraction
    result = num1 - num2;

    // Display the result
    printf("The result of %d - %d is %d\n", num1, num2, result);

    return 0;
}

Explanation of the Code

1. Include the Standard I/O Header: The #include <stdio.h> directive includes the standard input/output library necessary for printf().
2. Declare Variables: int num1, num2, result; declares three integer variables.
3. Initialize Variables: num1 is set to 10, and num2 is set to 5.
4. Perform Subtraction: result = num1 - num2; computes the difference between num1 and num2.
5. Display the Result: The printf() function outputs the result to the console.

This method is ideal for basic subtraction operations where the numbers are hardcoded into the program.

Method 2) Subtraction of two numbers in C using User-Defined Functions

To enhance code reusability and modularity, you can encapsulate the subtraction logic within a function. Here’s how you can do it:

Code Example

#include <stdio.h>

// Function declaration
int subtract(int a, int b);

int main() {
    int num1, num2, result;

    // Prompt user for input
    printf("Enter two numbers: ");
    scanf("%d %d", &num1, &num2);

    // Call the subtraction function
    result = subtract(num1, num2);

    // Display the result
    printf("The result of %d - %d is %d\n", num1, num2, result);

    return 0;
}

// Function definition
int subtract(int a, int b) {
    return a - b;
}

Explanation of the Code

1. Function Declaration: int subtract(int a, int b); declares a function that takes two integers and returns their difference.
2. Function Definition: The subtract() function implements the subtraction operation and returns the result.
3. User Input: scanf("%d %d", &num1, &num2); reads two integers from the user.
4. Function Call: result = subtract(num1, num2); calls the subtract() function with user-provided values.

This method is beneficial when you want to reuse the subtraction logic in different parts of your program or across multiple programs.

Method 3) Subtraction of two numbers in C using Pointers

Pointers provide a way to work with memory addresses, and you can use them to perform subtraction.

Code Example

#include <stdio.h>

// Function declaration
void subtract(int *a, int *b, int *result);

int main() {
    int num1, num2, result;

    // Prompt user for input
    printf("Enter two numbers: ");
    scanf("%d %d", &num1, &num2);

    // Call the subtraction function using pointers
    subtract(&num1, &num2, &result);

    // Display the result
    printf("The result of %d - %d is %d\n", num1, num2, result);

    return 0;
}

// Function definition
void subtract(int *a, int *b, int *result) {
    *result = *a - *b;
}

Explanation of the Code

1. Function Declaration: void subtract(int *a, int *b, int *result); declares a function that uses pointers to perform the subtraction.
2. Function Definition: *result = *a - *b; dereferences the pointers to access the values, performs the subtraction, and stores the result.
3. Function Call: subtract(&num1, &num2, &result); passes the addresses of num1, num2, and result to the function.

This method is particularly useful when dealing with more complex data structures or when you need to modify multiple variables simultaneously.