Yours, Etc.: Origins and Uses of 8 Sign-Offs
End Of File
1. The out-of-band value returned by C's sequential character-input functions (and their equivalents in other environments) when end of file has been reached. This value is -1 under C libraries postdating V6 Unix, but was originally 0.
2. The keyboard character (usually control-D, the ASCII EOT (End Of Transmission) character) that is mapped by the Unix terminal driver into an end-of-file condition.