The IO Classes

• IO library types and headers (wchar_t versions begin with a w):

• IO type objects cannot be copied or assigned.
• Reading or writing an IO object changes its state.
• IO library condition states and ways to interrogate the state of flags:
  • iostate values are sets of bit flags representing different errors.

• Conditions that cause the buffer to be flushed:
  • The program completes normally (returns from main). Buffers are not flushed if the program crashes.
  • The buffer becomes full.
  • The buffer is flushed explicitly (endl: adds a newline, flush: no new data, ends: adds a null, etc.).
  • unitbuf is used to set the internal state to empty the buffer after each output: cout << unitbuf / nounitbuf. unitbuf is set for cerr by default.
  • If it is tied to another stream (cin, cerr are tied to cout), reading or writing on other streams will flush the tied output stream. Streams has two overloaded tie member functions: tie() returns the stream it’s tied to, and tie(s) ties itself to s.

File Input and Output

• Operations specific to fstream:

• ifstream and ofstream inherit from istream and ostream.
• If a call to open fails, failbit is set, and we can use if (out) to check if it succeeded.
• fstream objects are automatically closed if out of scope.
• File Modes (preceded with a scope ofstream::/ifstream::):
  • Default mode for ofstream is out and trunc.

string Streams

• Operations specific to stringstream for quick input and output:

PersonInfo info;            // create an object to hold this record's data 
istringstream record(line); // bind record to the line we just read 
record >> info.name;        // read the name
while (record >> word)      // read the phone numbers and store them
    info.phones.push_back(word);