DEFINITION MODULE Termbase ; (* Initially the read routines from Keyboard and the write routine from Display is assigned to the Read, KeyPressed and Write procedures. *) EXPORT QUALIFIED ReadProcedure, StatusProcedure, WriteProcedure, AssignRead, AssignWrite, UnAssignRead, UnAssignWrite, Read, KeyPressed, Write ; TYPE ReadProcedure = PROCEDURE (VAR CHAR) ; WriteProcedure = PROCEDURE (CHAR) ; StatusProcedure = PROCEDURE () : BOOLEAN ; (* AssignRead - assigns a read procedure and status procedure for terminal input. Done is set to TRUE if successful. Subsequent Read and KeyPressed calls are mapped onto the user supplied procedures. The previous read and status procedures are uncovered and reused after UnAssignRead is called. *) PROCEDURE AssignRead (rp: ReadProcedure; sp: StatusProcedure; VAR Done: BOOLEAN) ; (* UnAssignRead - undo the last call to AssignRead and set Done to TRUE on success. *) PROCEDURE UnAssignRead (VAR Done: BOOLEAN) ; (* Read - reads a single character using the currently active read procedure. *) PROCEDURE Read (VAR ch: CHAR) ; (* KeyPressed - returns TRUE if a character is available to be read. *) PROCEDURE KeyPressed () : BOOLEAN ; (* AssignWrite - assigns a write procedure for terminal output. Done is set to TRUE if successful. Subsequent Write calls are mapped onto the user supplied procedure. The previous write procedure is uncovered and reused after UnAssignWrite is called. *) PROCEDURE AssignWrite (wp: WriteProcedure; VAR Done: BOOLEAN) ; (* UnAssignWrite - undo the last call to AssignWrite and set Done to TRUE on success. *) PROCEDURE UnAssignWrite (VAR Done: BOOLEAN) ; (* Write - writes a single character using the currently active write procedure. *) PROCEDURE Write (VAR ch: CHAR) ; END Termbase.