Simpson's One-Third Rule of numerical integration in C

#include<stdio.h>

#include<conio.h>

float f(float x){

float r;

r=2*x+1;

return r;

}

void main(){

float output;

float a,b;

float h,s;

int i,j;

int n;

clrscr();

printf("===========================================\n");

printf("           SIMPSON'S ONE-THIRD RULE\n");

printf("===========================================\n");

printf("Enter the integral limit:-\n");

printf("-------------------------------------------\n");

printf("Lower limit value a: \n");

scanf("%f",&a);

printf("Upper limit value b: \n");

scanf("%f",&b);

printf("-------------------------------------------\n");

printf("Enter number of total intervals: \n");

scanf("%d",&n);

h=0.0;

h=(b-a)/(2*n);

printf("____________________________________________\n");

printf("Resultant value of h is %.2f \n",h);

s=0.0;

s=f(a)+f(b)+4*f(a+h);

printf("Resultant value of f(a) + f(b) is %.2f \n",s);

for (i=3;i<2*n;i+=2)

{

s+=2*f(a+(i-1)*h)+4*f(a+i*h);

}

printf("Resultant value of whole summation of f(-) is %.2f\n",s);

output=1;

output=(h/3)*s;

printf("Output value of the integral is %.2f \n",output);

printf("____________________________________________\n");

printf("             GOOD LUCK\n");

getch();

}