Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!OSU-20.IRCC.OHIO-STATE.EDU!JONES-D From: JONES-D@OSU-20.IRCC.OHIO-STATE.EDU (Dave Jones) Newsgroups: comp.os.vms Subject: Re: old prompt question which I never saw answered. Message-ID: <8806281241.AA21486@ucbvax.Berkeley.EDU> Date: 12 Jun 88 16:18:30 GMT References:Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 23 Mr. Haining's statements regarding how VMS issues prompts are wrong. Whether a prompt appears has nothing to do with whether SYS$INPUT is the same as SYS$OUTPUT. The prompt is written to SYS$INPUT ONLY if SYS$INPUT is a terminal, prompts are never sent to SYS$OUTPUT. The VMS terminal driver has a feature called read-with-prompt that treats the display of a prompt and reading of input as a single operation. DCL and most VMS utilities use read-with-prompt when reading from a terminal and a normal read when reading from a non-terminal (e.g. mailbox) device. An additional caveat about assigning SYS$INPUT to a mailbox is that DCL will 'read ahead' 1 record from the mailbox, so you can't simply use read attention AST's to synchronize processing of output to SYS$OUTPUT with the commands you are sending to SYS$INPUT. (Note that this disscussion concerns the operation of DCL and VMS utilities, user-written and third-party software may actually write their prompts using the write function.) ------ David Jones Ohio State University 1981 Neil Ave. Rm. 406 Columbus OH, 43210 -------