绝对的ｐｒｉｍｅｒ的源代码　值得珍藏。第五版　外加清华讲义　

				// if.cpp -- using the if statement
				#include 
				int main()
				{
				    using namespace std;
				    char ch;
				    int spaces = 0;
				    int total = 0;
				    cin.get(ch);
				    while (ch != '.')   // quit at end of sentence
				    {
				        if (ch == ' ')  // check if ch is a space
				            ++spaces;
				        ++total;        // done every time
				        cin.get(ch);
				    }
				    cout 				    cout 				    return 0;
				}