endOfInput

End of input, often abbreviated as end-of-input or EOF, is a condition that occurs when a data source has no more data to deliver. It is encountered in streams such as files, pipes, network connections, or interactive input. End of input is a state reported by the reading abstraction rather than a data value; programs typically detect it by examining the return value of read operations or by catching a corresponding exception or error.

How end of input is signaled varies by programming environment. In C, functions like getchar return the special value EOF (typically -1) when no more data can be read. In Java, a reader’s readLine method returns null at end of stream. In Python, input and most file iteration raise EOFError or terminate a loop when the underlying iterator is exhausted. In many languages, a read operation may return a boolean flag indicating success or failure, or an empty result when the end of input is reached. Terminal input also has a concrete user-driven signal: pressing Ctrl-D on Unix-like systems or Ctrl-Z on Windows typically causes an end-of-input condition, or the user can close a pipe or redirect.

End of input is distinct from an ordinary data value; it signals termination of the data source. Programs commonly use it to terminate loops that read until no more data remains, to perform necessary cleanup, or to switch to a different mode of operation. Proper handling often involves checking the return value or catching exceptions and ensuring resources are released appropriately.