bisection.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define f(x) ((x*x*x)-36)

int main(){
float a=0, b=0, error=0, m ,mold;
int i=0;
printf("Enter interval values: ");
scanf("%f %f",&a,&b);                      // interval is : [a,b]
if((f(a)*f(b))>0){                         
        printf("Invalid Interval");       //Means that there is no root of f(x) in the interval [a,b]
        exit(1);                                                        
}
else if(f(a)==0 || f(b)==0){
        printf("Root is one of interval bounds. Root is %f\n",f(a)==0?a:b);        
        exit(0);
}
printf("Iteration\ta\t\tb\t\tm\t\tf(m)\t\terror\n");
do{
        mold=m;
        m=(a+b)/2;                                                      //new root candidate
        printf("%2d\t%4.6f\t%4.6f\t%4.6f\t%4.6f\t",i++,a,b,m,f(m));
        if(f(m)==0){
                printf("Root is %4.6f\n",m);
        }else if ((f(a)*f(m))<0){
                b=m;
        }else a=m;
        error=fabs(m-mold);
        if(i==1){
                printf("----\n");
        }else printf("%4.6f\n",error);
}while(error>0.00005);                         //Stop condition (error>0.00005)
printf("Approximate Root : %4.6f",m);
return 0;
}