Bisection Method of Numerical Engineering using 3 stopping criterion. This program is for the equation (x-2)^2-log(x)=0. You can change it by changing the return statement in the function name "func".

FINAL_BISECTION_METHOD.CPP

#include<iostream>
#include<math.h>
#define e 2.718281828
#define pie 3.141592654
using namespace std;
double r;
int m;
float num;
double ea;
int flag;
char choice;
double func(double x)
{
   // return (pow(e,-x)*(3.2*(sin(x))-0.5*(cos(x))));
   //return(5*x*x*x-5*x*x+6*x-2);
   return(pow((x-2),2)-log(x));
}
void send(double c)
{
    r=c;
}
void mid(double a,double b,int m)
{
    long double c;
    if((abs(b-a))>=pow(10,-(m+1)))
    {
        if(func(a)*func(b)>=0)
        {
            cout<<"You have assumed the wrong initial values\n";
        }
        else
        {
            c=(a+b)/2;
            send(c);
            if(func(c)==0.0)
            {
                cout<<"The root is :"<<c<<endl;
            }
            else if(func(c)*func(a)<0)
            {
                mid(a,c,m);
            }
            else if(func(c)*func(b)<0)
            {
                mid(c,b,m);
            }
        }
    }
 }
void mid(double a,double b,float num)
{
    long double c;
    float temp=0;
    while(temp!=num)
    {
        if(func(a)*func(b)>=0)
        {
            flag=0;
        }
        else
        {
            flag=1;
            c=(a+b)/2;
            send(c);
            if(func(c)==0.0)
            {
                cout<<"The root is :"<<c<<endl;
            }
            else if(func(c)*func(a)<0)
            {
                b=c;
            }
            else if(func(c)*func(b)<0)
            {
                a=c;
            }
        }
        temp++;
    }
    if(flag==0){cout<<"You have assumed wrong initial values"<<endl;}
 }
void mid(double a,double b,double ea)
{
    long double c;
    long double temp=ea;
    long double pre=0;
    do
    {
        temp=abs((((a+b)/2)-pre)/((a+b)/2));
        if(func(a)*func(b)>=0)
        {
            flag=0;break;
        }
        else
        {
            flag=1;
            pre=(a+b)/2;
            c=(a+b)/2;
            send(c);
            if(func(c)==0.0)
            {
                cout<<"The root is :"<<c<<endl;
            }
            else if(func(c)*func(a)<0)
            {
                b=c;
            }
            else if(func(c)*func(b)<0)
            {
                a=c;
            }
        }
    }while(temp>=ea);
    if(flag==0){cout<<"You have assumed wrong initial values"<<endl;}
}
int main()
{
   do
   {
        double w,y;
        cout<<"Enter the initial values of the function"<<endl;
        cin>>w;
        cin>>y;
        int ch;
        cout<<"Enter through which stopping criteria you wanna proceed.\n1-By Significant Digit\n2-By number of iteration\n3-By relative error\n";
        cin>>ch;
        switch(ch)
        {
            case 1:
            {
                cout<<"Enter to how many decimal digits you want answer :";
                cin>>m;
                mid(w,y,m);
                r = ((double)((int)(r *pow(10,m))))/pow(10,m);
                cout<<"The root is: "<<r<<endl;
                break;
            }
            case 2:
            {
                cout<<"Enter number iteration you wanna go :";
                cin>>num;
                mid(w,y,num);
                if(flag==0){}
                else{cout<<"The root is: "<<r<<endl;}
                break;
            }
            case 3:
            {
                cout<<"Enter the value of relative error(Without Percentage) :";
                cin>>ea;
                mid(w,y,ea);
                if(flag==0){}
                else{cout<<"The root is: "<<r<<endl;}
            }
        }
   cout<<"Press Y to do the process again"<<endl;
   cin>>choice;
   }while(choice=='y'||choice=='Y');
   return 0;
}