new to C++.. HELP!

[Scofield89]

im working on the following program,

#include <iostream.h>
#include <math.h>
void main()
{
    float x,y,z;
    int s;
    bool b;

    cout<<"x"<<'\n';
    cin>>x;
    cout<<"y"<<'\n';
    cin>>y;
    cout<<"s"<<'\n';
    cin>>s;
    if(x==y)

            z =0.9;
            else

                    z=0.8;

            cout<<"z="<<z<<"\n";

            b=s%100;

            cout<<"b="<<b<<'\n';
    x=3;

    for(int i=1;i<=3;i++)

    {
    x*=2;

    cout<<" "<<i<<" "<<x<<'\n';
    }
}

and it gives me 3 warnings:
truncation from 'const double' to 'float' twice and forcin value to bool 'true' or 'false'