Type for stream state flags.
  Bitmask type to store stream error state flags. The flag values can be any combination of the following constant member values:

bit	indicates
ios_base::badbit	Loss of integrity of stream buffer.
ios_base::eofbit	End-Of-File reached while extracting from an input sequence.
ios_base::failbit	Last input operation failed before completion.
ios_base::goodbit	No error. Represents the absence of all the above.

See also.
  ios_base class