C program to implement Simpson's 3/8 rule

Ex:

Formula:

here a=0, b=6 and h=1

x	0	1	2	3	4	5	6
y=f(x)	1	.50	.33	.25	.20	.16	.14

Now apply Simpson's 3/8 rule:

f(x)= 3/8[(1+.14)+3(.50+.33+.20+.16)+2(.25)]
     =3/8[1.14+3.57+.50]
     =3/8(5.21)  =1.95


C Code:

#include<stdio.h>
float f(float );

void main()
{ float a,b,h,i,div3=0,o=0,fy;
int y=1;
printf("\nEnter the lower and upper limit of a function");
scanf("%f%f",&a,&b);
printf("\nEnter the difference");
scanf("%f",&h);
printf("\nx\t f(x)");
for(i=a;i<=b;i=i+h)
{ printf("\n%f\t%f",i,f(i));
}
for(i=a+h;i<=b-h;i=i+h)
{ if(y%3==0)
div3=div3+f(i);
else
o=o+f(i);
y++;
}
fy= 3*h/8*(f(a)+f(b)+3*(o)+2*(div3));
printf("\nIntegral=%f",fy);
}

float f(float x)
{
return(1/(1+x));
}

Output:

Enter the lower and upper limit of a function 0                                                                                     

6                                                                                                    

Enter the difference 1                                                                                                                        

x               f(x)                                                                                                                

0.000000        1.000000                                                                                                         

1.000000        0.500000                                                                                                         

2.000000        0.333333                                                                                                         

3.000000        0.250000                                                                                                         

4.000000        0.200000                                                                                                         

5.000000        0.166667                                                                                                         

6.000000        0.142857                                                                                                         

Integral=1.966072