c++ primer plus 习题6.1 （cctype，cin.get）

#include<iostream>
#include<cctype>
using namespace std;
int main() {
char ch,change;
cout<<"please input:";
cin.get(ch);
while(ch != '@'){
if(!isdigit(ch)){
if(isupper(ch))
{
change=ch+32;
cout<<change;
}
if(islower(ch))
{	change=ch-32;
cout<<change;
}
if((!isupper(ch))&&(!islower(ch)))
cout<<ch;

}

cin.get(ch);
}
return 0;
}