Simpson's 1/3rd Rule

 #include<stdio.h>  
 float integrate(float);  
 void main()  
 {  
      float a,b,h,n,sum=0;  
      int i;  
      printf("\n\tINTEGRATION THROUGH SIMPSON' 1/3 RULE");  
      printf("\n\t====================================");  
      printf("\n\nEnter the upper limit a ");  
      scanf("%f",&a);  
      printf("\n\nEnter the lower limit b ");  
      scanf("%f",&b);  
      printf("\n\nEnter the number of sub-intervals ");  
      scanf("%f",&n);  
      h=(b-a)/n;  
      sum=integrate(a)+integrate(b);  
      for(i=1;i<n;i++)  
      {  
           if(i%2==0)  
                sum=sum+(2*integrate(a+i*h));  
           else  
                sum=sum+(4*integrate(a+i*h));  
      }  
      sum=sum*(h/3);  
      printf("\nThe value of integral is %f",sum);  
 }  
 float integrate(float n)  
 {  
      return 1/(1+(n*n));  
 }