Program for Definite Integration in C++

#include <stdio.h>
#define X 1000

void main(void)
{
 float i, p, q, total = 0;
 printf("\nThis program will integrate p function between two boundary limits.");
 printf("\n\nEnter the first boundary limit:");
 scanf("%f", &p);
 printf("\nEnter the second boundary limit:");
 scanf("%f", &q);
 if(p > q) { i = p; p = q; q = i; }

 for(i = p; i < q; i += (q - p) / X)
 {
  y = x * x + 2 * x - 4;
  total += y * (q - p) / X;
 }

 printf("\n\nValue of integration is:%.3f", total);
 getch();
 return;
}