A function call is an important part of the C programming language. It is called inside a program whenever it is required to call a function. It is only called by its name in the main() function of a program. We can pass the parameters to a function calling in the main() function.
Syntax :
#include <stdio.h>
int add(int a, int b);
void main()
{
int sum;
int a, b;
printf(" Enter the first and second number \n");
scanf("%d %d", &a, &b);
sum = add(a, b); // call add() function
printf( "The sum of the two number is %d", sum);
}
int add(int n1, int n2) // pass n1 and n2 parameter
{
int c;
c = n1 + n2;
return c;
}
Output :
Enter the first and second number
5
6
The sum of the two number is 11
Call by value
When single or multiple values of an actual argument are copied into the formal parameter of a function, the method is called the Call by Value. Hence, it does not alter the function's actual parameter using the formal parameter.
Consider a program to demonstrate the Call by Value in C programming.
#include <stdio.h> int main()
{
int x = 10, y = 20;
printf (" x = %d, y = %d from main before calling the function", x, y);
CallValue(x, y);
printf( "\n x = %d, y = %d from main after calling the function", x, y);
}
int CallValue( int x, int y)
{
x = x + 5;
y = y + 5;
printf (" \nx = %d, y = %d from modular function", x, y);
}
Output :
x = 10, y = 20 from main before calling the function
x = 15, y = 25 from modular function
x = 10, y = 20 from main after calling the function
Call by reference
In this method, the address of the actual argument is copied into the function call's formal parameter; the method is known as Call by Reference. If we make some changes in the formal parameters, it shows the effect in the value of the actual parameter.
Consider a program to demonstrate the Call by Reference in C programming.
#include <stdio.h> int main()
{
int x = 10, y = 20;
printf (" x = %d, y = %d from main before calling the function", x, y);
CallValue (&x, &y);
printf( "\n x = %d, y = %d from main after calling the function", x, y);
}
int CallRef( int *a, int *b)
{
*a = *a + 5;
*b = *b + 5;
printf (" \nx = %d, y = %d from modular function", *a, *b);
}
Output :
x = 10, y = 20 from main before calling the function
x = 15, y = 25 from modular function
x = 15, y = 25 from main after calling the function
