#include<iostream.h>
#include <stdlib.h>
void main()
{
    cout<<"欢迎使用"<<endl;
    char ch,p;
    cout<<"=====================\n";
    cout<<"    a取钱"<<endl;
    cout<<"    b存钱"<<endl;
    cout<<"    c查询余额"<<endl;
    cout<<"    d取卡"<<endl;
    cout<<"=====================\n";
    cout<<"请输入你想执行的:";
    cin>>ch;    
    while(ch!='a'&&ch!='b'&&ch!='c'&&ch!='d')
    {
        cout<<"你输入有误,请重新输入";
        cin>>ch;
    }
    cout<<"======================!";
    int i,j;
    system("cls");

    while(ch!='d')
    {
        switch(ch)
        {
        case'a':
            {
                cout<<"请选择你要取出的金额\n";
                cout<<"1.$50\n";
                cout<<"2.$100\n";
                cout<<"3.$200\n";
                 cout<<"4.退出  \n";
                cin>>p;
                while(p!='1'&&p!='2'&&p!='3'&&p!='4')
                {
                    cout<<"你输入有误,请重新输入";
                    cin>>p;
                }
                system("cls");

                switch(p)
                {
                case'1':cout<<"you gredit money is $50,thank you!\n";break;
                case'2':cout<<"you gredit money is $100,thank you!\n";break;
                case'3':cout<<"you gredit money is $200,thank you!\n";break;
                case'4':cout<<"thank you for using!\n";break;
                }
                break;                
            }
        case'b':
            {                
                int o;
                cout<<"请输入你要存人的数额:"<<endl;
                cin>>o;
            
                int w;
                cout<<"请输入帐号:"<<endl;
                cin>>w;
                cout<<"你存入了"<<o<<"到帐号"<<w<<endl;
                system("cls");
                cout<<"thank you for useing"<<endl;
                break;
            }
        case'c':
            {
                cout<<"你的余额为$1000\n";
                break;
                
            }
            
        }
        break;

        cout<<"thank you for  useing"<<endl;
    }
    
}

感觉里面有不好的地方．请高手指教下．．比如如何能在存钱里限制只能输入数字的限制．．