#include<math.h>
#include<stdlib.h>
#include<iostream.h>
class Calculator
{
    double a,b;
public:
    Calculator(){a=0;b=0;}; //could be omitted
    void newa()
    {
        double num;
        cout<<"Input the number:";
        cin>>num;
        a=num;
    }
    void newab()
    {
        double num1,num2;
        cout<<"Input the numbers.the first number:";
        cin>>num1;
        cout<<"Input the senond number:";        
        cin>>num2;
        a=num1;
        b=num2;
    }
    double Geta(){return a;}
    double Getb(){return b;}
    double Add(Calculator &A);
    double Sub(Calculator *A);
    double Mul(Calculator &A);
    double Div(Calculator &A);
    double Sin(Calculator &A);
    double Cos(Calculator &A);
    double Tan(Calculator &A);
    double Exp(Calculator &A);
    double Fabs(Calculator &A);
    double LogE(Calculator &A);
    double Log10(Calculator &A);
    double Pow(double x,double y);
    double Sqrt(double x);
};
double Calculator::Add(Calculator &A)
{
    return A.a+A.b;
}
double Calculator::Sub(Calculator *A)
{
    return A->a-A->b;
}
double Calculator::Mul(Calculator &A)
{
    return A.a*A.b;
}
double Calculator::Div(Calculator &A)
{
    if(A.b==0)
    {cout<<"Error! The program will be terminated!"<<endl;exit(0);}
    return A.a/A.b;
}
double Calculator::Sin(Calculator &A)
{
    return sin(A.a);
}
double Calculator::Cos(Calculator &A)
{
    return cos(A.a);
}
double Calculator::Tan(Calculator &A)
{
    return tan(A.a);
}
double Calculator::Exp(Calculator &A)
{
    return exp(A.a);
}
double Calculator::Fabs(Calculator &A)
{
    return fabs(A.a);
}
double Calculator::LogE(Calculator &A)
{
    return log(A.a);
}
double Calculator::Log10(Calculator &A)
{
    return log10(A.a);
}
double Calculator::Pow(double x,double y)
{
    return pow(x,y);
}
double Calculator::Sqrt(double x)
{
    if(x<0)
    {cout<<"Error! The program will be terminated!"<<endl;exit(0);}
    return sqrt(x);
}

void main()
{
    int sel;
    Calculator cal;
    cout<<"Welcome to use the calculator!please select."<<endl;
    cout<<"1:\'+\'    2:\'-\'     3:\'*\'      4:\'/\'     5:\'sin\'   6:\'cos\'  7:\'tan\'"<<endl;
    cout<<"8:\'exp\'  9:\'fabs\'  10:\'logE\'  11:\'log10\' 12:\'pow\'  13:\'sqrt\'"<<endl;
    do
    {
    cout<<"Please select:(0--exit)";
    cin>>sel;
    switch (sel)
    {
    case 0: break;
    case 1: cal.newab();
            cout<<"The result is:"<<cal.Add(cal)<<endl;
            break;
    case 2: cal.newab();
            cout<<"The result is:"<<cal.Sub(&cal)<<endl;
            break;
    case 3: cal.newab();
            cout<<"The result is:"<<cal.Mul(cal)<<endl;
            break;
    case 4: cal.newab();
            cout<<"The result is:"<<cal.Div(cal)<<endl;
            break;
    case 5: cal.newa();
            cout<<"The result is:"<<cal.Sin(cal)<<endl;
            break;
    case 6: cal.newa();
            cout<<"The result is:"<<cal.Cos(cal)<<endl;
            break;
    case 7: cal.newa();
            cout<<"The result is:"<<cal.Tan(cal)<<endl;
            break;
    case 8: cal.newa();
            cout<<"The result is:"<<cal.Exp(cal)<<endl;
            break;
    case 9: cal.newa();
            cout<<"The result is:"<<cal.Fabs(cal)<<endl;
            break;
    case 10: cal.newa();
            cout<<"The result is:"<<cal.LogE(cal)<<endl;
            break;
    case 11: cal.newa();
            cout<<"The result is:"<<cal.Log10(cal)<<endl;
            break;
    case 12: cal.newab();
            cout<<"The result is:"<<cal.Pow(cal.Geta(),cal.Getb())<<endl;
            break;
    case 13: cal.newa();
            cout<<"The result is:"<<cal.Sqrt(cal.Geta())<<endl;
            break;
    default: cout<<"Your selection is ERROR! Select again!"<<endl;
    }
    }while(sel!=0);
}
本人水平有限！有错误请指正！谢谢