source file name: simpint.c 

void main()

{

long P,N,R;

long SI;

clrscr();

printf("\n enter deposited Amount(P) , rate (R) and no. of years(N): ");

scanf("%ld%ld%ld",&P,&N,&R);

SI=(P*N*R)/100;

printf("\n Simple interest=Rs.%ld  ",SI);

getch();

}

Output:

1.  enter deposited Amount(P) , rate (R) and no. of years(N):

20000 5 3

Simple interest=Rs. 3000

2.  enter deposited Amount(P) , rate (R) and no. of years(N):

25000 7 4

Simple interest=Rs. 7000