#include <iostream>
#include <math.h>

int add(int n, int m);
int add1(int& n, int& m);
int add2(int* n, int* m);
void voidadd(int& n, int& m);
void voidadd0(int n, int m);

long double Sqrt(long double x, long double accuracy=0.1);

int main()
{
        int i,j,k,l,m, n;
        long double a;
        j=0, k=0, l=m=n=0;
        for(i = 1; i<101;++i )
        {
           j=add(i,j);
           k=add1(i,k);
           l=add2(&i,&l);
//         l=add2(*i,*l);   /** this is error*/
           voidadd(i,m);
           voidadd0(i,n);
        }
        std::cout<<"sum of 1 to 100 = " << j<<", " << k
        << ", " << l << ",void type  " << m << ", " << n << std::endl;
//------------------default values of arguments ----------------
        a = Sqrt(10.);
        std::cout << "Sqrt(10) with default accuracy = " << a << std::endl;
        a = Sqrt(10., 0.00001);
        std::cout << "Sqrt(10) with accuracy of 0.00001 = " << a << std::endl;
        return 999;
}

int add(int n, int m) { int j = n + m; return j; }
int add1(int& n, int& m) { int j = n + m; return j; }
int add2(int* n, int* m) { int j = *n + *m; return j; }
void voidadd0(int n, int m) { m = n + m; return ; }
void voidadd(int &n, int &m) { m = n + m; return ; }

long double Sqrt(long double x, long double accuracy)
{
        long double newSqrt = x/2, oldSqrt=0;

        if(x < 0) {
                std::cout <<"x negative not allowed" << std::endl;
                exit(1);
        }
        while (fabs(newSqrt-oldSqrt) > accuracy) {
        oldSqrt = newSqrt;
        newSqrt = 0.5 * (oldSqrt + x/oldSqrt);
        }
        return newSqrt;
}

---------------------------------------------------------------

./a.exe
sum of 1 to 100 = 5050, 5050, 5050,void type  5050, 0
Sqrt(10) with default accuracy = 3.16232
Sqrt(10) with accuracy of 0.00001 = 3.16228