Actual argument:The arguments used in calling functions are called as actual arguments. Formal argument:The arguments used in called or user defined functions are called as formal arguments.

Call by value:In this type the value of actual arguments are passed to the formal arguments and the operation is done on the formal arguments.

Any change made in the formal argument does not effect actual arguments because formal arguments are photocopy of actual arguments. So when a function is called by call by value method, it doesnt effect the actual contents of the actual arguments

Changes made in the formal arguments are local to the block of called function. Once control return back to the calling function the changes made vanish.

In call by value method the actual and formal argument are stored at different memory locations so both are not same.

The following program illustrate the concept of call by value method.

#include#includevoid swap(int , int );void main(){int a=5,b=10;clrscr();printf("\nBefore swapping \n a = %d , b = %d",a,b);swap(a,b); // a,b are actual argumentgetch();}void swap(int a, int b) // this a and b are formal arguments.{int z;z=a;a=b;b=z;printf("\nIn swap function \n a = %d , b = %d",a,b);}

OUTPUT:Before swapping a = 5 , b = 10In swap function a = 10 , b = 5Call by reference: In this type instead of passing values, addresses are passed. Function operates on addresses rather than values. Here the formal arguments are pointers to the actual arguments. In this type formal argument points to the actual argument.

Hence changes made in the argument are permanent.In call by reference the actual and formal argument are pointing to the same memory locations so both are same.The following program illustrate the concept of call by reference method.

#include#includevoid swap(int * , int *);void main(){int a=5,b=10;clrscr();printf("\nBefore swapping \n a = %d , b = %d",a,b);swap(&a,&b);getch();}void swap(int *a, int *b){int z;z=*a;*a=*b;*b=z;printf("\nIn swap function \n a = %d , b = %d",*a,*b);}

OUTPUT:Before swapping a = 5 , b = 10In swap function a = 10 , b = 5// Sum of series using function with return type with argument#include#includeint sum1(int );void main(){int n,d;printf(Enter number upto which u want to print series:);scanf("%d",&n);d=sum1(n);printf("\nsum is %d",d);getch();}int sum1(int n){ int i=1,sum=0; while(i