标准输入输出

In the following, in is an istream (cin), out is an ostream (cout, cerr, clog), i is int, c is char, and cp is char*.

  in >> x;               // Read 1 word to numeric, string, or char* x, return in
  in.get();              // Read 1 char (0-255) or EOF (-1) as an int
  in.get(c);             // Read 1 char into c, return in
  in.unget();            // Put back last char read, return in
  in.getline(cp, i);     // Read up to i chars into char cp[i] or until ‘\n‘, return in
  in.getline(cp, i, c);  // Read to c instead of ‘\n‘, return in
  getline(in, s);        // Read up to ‘\n‘ into string s, return in
  in.good();             // true if no error or EOF
  bool(in);              // in.good();
  in.bad();              // true if unexpected char in formatted input
  in.clear();            // Allow more input after bad, or throw an ios::failure
  in.eof();              // true if end of file
  in.fail();             // true if system input error

  out << x;                // Formatted output, redirected with >
  out << endl;             // Print ‘\n‘ and flush
Input with >> reads a contiguous sequence of non-whitespace characters. If x is numeric and the next word contains invalid characters (such as "1.5" or "foo" for an int), then the first offending character remains unread, in.bad() is set, and no further input can occur until in.clear() is called. Input into a char* array is not bounds checked. Input returns the istream to allow chaining, and has a conversion to bool to test for success. Output also returns the ostream to allow chaining.

  // Read and print pairs of strings and ints until something goes wrong
  // Input:  hi 3 there 5 this is 1 test
  // Output: hi 3
             there 5

  string s; int i;
  while (cin >> s >> i)
    cout << s << " " << i << endl;
  cin.clear();
The get() methods read one character including whitespace. The various getline() functions read up through the next newline character and discard the newline. The methods good(), bad(), eof(), fail(), clear(), and implicit conversion to bool are available in ostream, just as in istream, but are seldom used.