In C programming, the call by value mechanism is used to pass arguments to functions. When a function is called by value, a copy of the actual argument's value is made and passed to the function. This means that the function operates on a copy of the variable, not on the original variable itself.

Example

Here's a simple example to illustrate call by value:

#include <stdio.h>

// Function that takes an integer argument by value
void modifyValue(int x) {
    x = x + 10; // Modify the copy of the value
    printf("Inside function: x = %d\n", x);
}

int main() {
    int a = 5;
    printf("Before function call: a = %d\n", a);
    
    modifyValue(a); // Pass the value of 'a' to the function
    
    printf("After function call: a = %d\n", a); // 'a' is unchanged
    return 0;
}

Output

Before function call: a = 5
Inside function: x = 15
After function call: a = 5

Explanation

• a is passed to modifyValue function.
• Inside modifyValue, x is a copy of a. Modifying x does not affect a in main.
• The original variable a remains unchanged outside the function.

Advantages

1. Safety: The original values of the arguments cannot be altered by the function. This ensures that the caller’s data is protected from unintended modifications.
2. Simplicity: Call by value is straightforward and easier to understand because it operates on copies of the values.