Function Argumants - Call By Value

Call by value

• "Call by value" is a method of passing arguments to a function in C in which the function receives a copy of the values of the arguments, rather than a reference to the original arguments.

• This means that any changes made to the arguments within the function will not affect the values of the original arguments outside the function.

• When a function is called with "call by value", the values of the arguments are passed to the function, and the function receives a separate copy of these values.

• This allows the function to operate on the values of the arguments without modifying the original arguments.

Call by value - Example

Here's an example of call by value in C:

#include <stdio.h>

void swap(int x, int y)
{
    int temp;
    temp = x;
    x = y;
    y = temp;
}

int main()
{
    int a = 3, b = 5;
    printf("Before swapping: a = %d, b = %d\n", a,
           b);  // Print the values of a and b before the swap
    swap(a, b); // Call the swap function with call by value
    printf("After swapping: a = %d, b = %d\n", a,
           b); // Print the values of a and b after the swap
    return 0;
}

Output:

Explanation

• The swap function takes two integer arguments x and y, and swaps their values.

• When the function is called from the main function with call by value, the values of a and b are passed to the function and the function receives separate copies of these values.

• Within the swap function, the values of x and y are swapped, but the values of a and b in the main function remain unchanged.

Call by value - Another Example

Here's another example of call by value in C:

#include <stdio.h>

int square(int x)
{
    return x * x;
}

int main()
{
    int num = 5;
    printf("Before calling the function: num = %d\n",
           num);              // Print the value of num before the function call
    int result = square(num); // Call the square function with call by value
    printf("After calling the function: num = %d\n",
           num); // Print the value of num after the function call
    printf("Result of the function: %d\n",
           result); // Print the result of the function
    return 0;
}

Output:

Explanation

• The square function takes an integer argument x and returns its square.

• When the function is called from the main function with call by value, the value of num is passed to the function, and the function receives a separate copy of this value.

• Within the square function, the value of x is squared and the result is returned.

• However, the value of num in the main function remains unchanged.

When to use Call by value

• When the caller does not want the function to modify the original values: This allows the caller to use the original values for other purposes after the function call, without being affected by any changes made by the function.

• When the function does not need to modify the values of its arguments, but only needs to perform some calculation or processing based on the values.

• For example: When finding the square of a number, it is not necessary to modify the original number, and call by value can be used to pass the number to the function.

• Appropriate for passing values of simple data types, such as integers, floating-point numbers, and characters. In such cases, creating a copy of the values and passing them to the function is relatively efficient and does not result in any significant overhead.

other methods

Please note, in situations where the function needs to modify the values of its arguments, "call by value" may not be appropriate, and other methods of argument passing, such as "call by reference" or "call by pointer", should be used.