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;}