In the C standard library, the character-reading functions such as getchar return a value equal to the symbolic value (macro) EOF to indicate that an end-of-file condition has occurred.
By default, the driver converts a Control-D character at the start of a line into an end-of-file indicator.
In DOS and Windows (and in CP/M and many DEC operating systems such as the PDP-6 monitor,[3] RT-11, VMS or TOPS-10[4]), reading from the terminal will never produce an EOF.
Some MS-DOS programs, including parts of the Microsoft MS-DOS shell (COMMAND.COM) and operating-system utility programs (such as EDLIN), treat a Control-Z in a text file as marking the end of meaningful data, and/or append a Control-Z to the end when writing a text file.
The reflective strip that was used to announce impending physical end of tape was also called an EOT marker.