Explain the concept of call by reference, with suitable code in C for each. Give advantage and disadvantage of call by reference

Word Count : 869

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In programming, *Call by Reference* is a method of passing arguments to a function. Instead of passing a copy of the variable (as in call by value), the address (reference) of the variable is passed. This allows the function to modify the actual value of the variable in the caller's scope.

### Concept of Call by Reference

When a function is called using *call by reference*, the function receives the reference (memory address) of the arguments, which means any changes made to the parameter within the function will directly affect the actual argument in the calling function. This is different from *call by value*, where the function only works with a copy of the argument, and modifications within the function do not affect the original variable.

In C, call by reference is implemented using pointers. A pointer is a variable that stores the address of another variable, allowing direct manipulation of the variable's value.

### Call by Reference in C

In C, to implement call by reference, we pass the address of the variable to the function using pointers. Here is an example:

```c
#include <stdio.h>

void add(int *a, int *b) {
    *a = *a + *b;  // Modify the value of 'a' directly
}

int main() {
    int x = 5, y = 10;

    printf("Before calling function: x = %d, y = %d\n", x, y);
    add(&x, &y);  // Passing the addresses of x and y

    printf("After calling function: x = %d, y = %d\n", x, y);
    return 0;
}
```

### Explanation:
- The function `add()` takes two pointer arguments (`int *a, int *b`).
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Degree : PG DIPLOMA PROGRAMMES
Course Name : POST GRADUATE DIPLOMA IN COMPUTER APPLICATIONS
Course Code : PGDCA_NEW
Subject Name : Programming in C and PYTHON
Subject Code : MCS 201
Year : 2023