C++ Primer Plus

Stream States

Let’s take a closer look at what happens for inappropriate input. A cin or cout object contains a data member (inherited from the ios_base class) that describes the stream state. A stream state (defined as type iostate, which, in turn, is a bitmask type, such as described earlier) consists of the three ios_base elements: eofbit, badbit, and failbit. Each element is a single bit that can be 1 (set) or 0 (cleared). When a cin operation reaches the end of a file, it sets eofbit. When a cin operation fails to read the expected characters, as in the earlier example, it sets failbit. I/O failures, such as trying to read a non-accessible file or trying to write to a write-protected disk, also can set failbit to 1. The badbit element is ...