X3J3/96-164
                                                           Page 1 of 1

Date:     November 10, 1996
To:       X3J3
From:     Rich Bleikamp
Subject:  ASYNC I/O and INQUIRE

Paper 96-158r2 described the syntax and edits for  asynchronous I/O.

One more piece of functionality is required: a way to ask about a pending I/O
operation, to see if it has completed, without actually waiting for completion.

Two obvious alternatives are:

1. Add a  NOWAIT keyword and a STATUS=char-variable specifier to the WAIT
statement.   If the pending I/O operation was already completed, then WAIT
would return “PENDING” or “COMPLETE”  in the char-variable (or a
processor defined value if the handle was not an active handle).  This  has
the advantage that no additional statements, such as INQUIRE, are possibly
I/O data transfer statements, or can wait for pending I/O.

OR

2. Extend INQUIRE with  HANDLE=value and  PENDING=char-variable
phrases.  The user would have to specify the unit #, the handle, and
INQUIRE would return “YES” or “NO” in the char-variable specified in the
PENDING=specifier.

The disadvantage of extending INQUIRE is that it then becomes another
possible WAIT operation and a data transfer statement (unless we still
require a WAIT even when PENDING returns a “NO”).   This clutters the
discussion of WAIT operations and data transfers even more, but may be
less confusing than a WAIT statement with a NOWAIT keyword.