6. I/O Stream States

Condition	Meaning
cin.good() == true	operation succeeded; !cin.good() is usually abbreviated as !cin (pronounced as "if cin is not good, then...")
cin.eof() == true	operation succeeded; the end of file was encountered; nothing else is left to input.
cin.fail() == true	nothing wrong with cin; however, the input formatting has failed, (as when reading "abc" when 123 was expected.) The program should try to recover and continue.
cin.bad() == true	something really bad happened to cin; cin is no longer usable and should be abandoned. No recovery is possible.

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