Re: HELP

[CONDIC@PSAVAX.PWFL.COM]

From: Marin David Condic, 407.796.8997, M/S 731-93
Subject: Re: Re: HELP
Original_To:  PROFS%"SMTP@PWAGPDB"
Original_cc:  CONDIC



>dewar@cs.nyu.edu (Robert Dewar) writes:
>
>>Time for another reminder. It is useless to ask questions about features
>>like this that are implementation dependent unless you tell us what
>>compiler you are using, what version, what operating system, what
>>machine etc.
>
>I am using DEC ada and I think it is Ada 83 compiler.
>
I believe that the original question was how to read a single
character input from the keyboard. Given that you're using DEC
Ada83, I can tell you how we have dealt with it. One method is to
rely on the DEC OS calls in the SMG library. (This involves more
than a simple call, since you first have to set up a sort of
pseudo-windowing environment that tries to make a VT terminal
behave more like Motif!) Anyway, the relavent call can be
interfaced with as follows:

===============================================================================
=

-------------------------------------------------------------------------------
    --  Read a Single Character
    --
    --  SMG$READ_KEYSTROKE status, keyboard_id, word_terminator_code
    --          [,prompt_string] [,timeout] [,display_id], [,rendition_set]
    --          [,rendition_compliment]
    --
    --  status          = Return status of call
    --  keyboard_id     = id of the virtual keyboard you are reading from
    --  prompt_string   = string used for prompt
    --  timeout         = if specified, any character typed before time_out
    --                    is returned in the buffer
    --  display_id      = id of the virtural display
    --  rendition_set   = video attributes for text
    --  rendition_compliment    = video attributes for text
    --

-------------------------------------------------------------------------------

    procedure SMG_READ_KEYSTROKE (
        STATUS                  : out CONDITION_HANDLING.COND_VALUE_TYPE;
        KEYBOARD_ID             : in KEYBOARD_TYPE;
        WORD_TERMINATOR_CODE    : out UNSIGNED_WORD;
        PROMPT_STRING           : in STRING := STRING'NULL_PARAMETER;
        TIMEOUT                 : in INTEGER := INTEGER'NULL_PARAMETER;
        DISPLAY_ID              : in DISPLAY_TYPE :=
DISPLAY_TYPE'NULL_PARAMETER;
        RENDITION_SET           : in SYSTEM.UNSIGNED_LONGWORD :=
SYSTEM.UNSIGNED_LONGWORD'NULL_PARAMETER;
        RENDITION_COMPLIMENT    : in SYSTEM.UNSIGNED_LONGWORD :=
SYSTEM.UNSIGNED_LONGWORD'NULL_PARAMETER

    pragma INTERFACE (VAXRTL, SMG_READ_KEYSTROKE);
    pragma IMPORT_VALUED_PROCEDURE (
        INTERNAL => SMG_READ_KEYSTROKE,
        EXTERNAL => "SMG$READ_KEYSTROKE",
        PARAMETER_TYPES => (COND_VALUE_TYPE, UNSIGNED_LONGWORD,
                            UNSIGNED_WORD, STRING, INTEGER,
                            UNSIGNED_LONGWORD, UNSIGNED_LONGWORD,
                            UNSIGNED_LONGWORD),
        MECHANISM => (VALUE, REFERENCE, REFERENCE, DESCRIPTOR,
                      REFERENCE, REFERENCE, REFERENCE, REFERENCE));

===============================================================================

I believe this call is duplicated in a package DEC provides
called "SMG" (appropriately enough!) Do an ACS command as follows

ACS> EXTRACT SOURCE/SPEC SMG

An alternate technique which only works moderately well, but does
provide for asynchronous keyboard/terminal behavior is to connect
an asynchronous system trap (AST) to a task entry and tie the AST
to the appropriate low level QIO routines. We've done this around
here and found that it can't always respond fast enough - but
it's still useful. How to do this is sufficiently complex that
I'd probably never give you a satisfying answer herin. Check the
VAX/VMS manuals on AST's and QIO's to understand how they work,
then check the DEC Ada manual to see how to connect an AST to a
task entry.

Pax Vobiscum,
Marin



Marin David Condic, Senior Computer Engineer    ATT:        407.796.8997
M/S 731-93                                      Technet:    796.8997
Pratt & Whitney, GESP                           Internet:   CONDICMA@PWFL.COM
P.O. Box 109600                                 Internet:   MDCONDIC@AOL.COM
West Palm Beach, FL 33410-9600
===============================================================================
    Glendower: "I can call spirits from the vasty deep."
    Hotspur: "Why so can I, or so can any man; but will they come when
    you do call for them?"

        -- Shakespeare, "Henry IV"
===============================================================================