Passing Parameter to a Function:

• In C Programming we have different ways of parameter passing schemes such as Call by Value and Call by Reference.
• Function is good programming style in which we can write reusable code that can be called whenever require.
• Whenever we call a function then sequence of executable statements gets executed. We can pass some of the information to the function for processing called argument.

Call by Value:

• In case of call by value the function is invoked by a calling function, by passing the actual values to be processed.
• This method copies the value of an argument into the formal parameters of the function.
• By default, C programming language uses call by value method to pass arguments.
• In general, this means that code within a function cannot alter the arguments used to call the function.
• In this method, the changes made to parameter have no effect on the argument.

Program:

#include <stdio.h>
#include <conio.h>
int main() {
    int a, b, ans;
    int sum(int x, int y);

    printf("Enter Two Values:);
    scanf("%d%d", &a, &b)

    ans=sum(a,b)

    printf("sum=%d",ans);
    getch();
}
int sum (int x, int y) {
    int z;
    z = x+y;
    return(z);
}

Output:

Enter Two Values: 10 20

Sum = 30

Call by Reference:

• In case of call by reference the function is invoked by a calling function, by passing the address of the actual values to be processed.
• In this method, the address of an argument is copied in the parameter.
• Inside the sub routine; the address is used to access the actual argument in the call.

Program:

#include <stdio.h>
#include <conio.h>
int main() {
int i, j;
int swap(int*x, int*y);
i=10;
j=20;
swap(&i, &j);
printf("%d%d", i, j);
    getch();
}
int swap (int*x, int*y) {
    int temp;
    temp = *y;
    *y = *x;
    *x = temp;
}

Output:

i=20

j=10