From: carl@SOL1.GPS.CALTECH.EDU (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: Re: Time functions in VMS comparing and returning the difference
Date: 4 Jan 1993 07:41:36 GMT
Organization: HST Wide Field/Planetary Camera
Distribution: world
Reply-To: carl@SOL1.GPS.CALTECH.EDU
NNTP-Posting-Host: sol1.gps.caltech.edu

In article <1992Dec21.211957.1409@galaxy.gov.bc.ca>, ewilts@galaxy.gov.bc.ca (Ed Wilts) writes:
>In article <921221000127.20407c7f@WSC.COLORADO.EDU>, STU011649835@WSC.COLORADO.EDU : The Macintosh Lab Manager : VIE Systems  writes:
>> 	My problem is figuring out how to compare 2 time values and find the
>> difference. I do not have access to the manuals ( if I did I would not know
>> where to start). The online help dosen't provide much help. If you
>> (anyone) have any sample programs, or anything else that might be of help,
>> PLEASE send..... Fortran, Pascal, Basic, C and DCl are all ok, but prefer
>> DCL programs. Thank you all.
>
>Quite a while back I posted the sources TIME to vmsnet.sources.  One of the
>archive sites should have this available.  It will allow you to easily compare
>2 times and return a delta-time.

Why go to user-written stuff?  This is another case of someone not reading
the on-line HELP.  In particular:

$ HELP RTL LIB LIB$SUB_TIMES

RTL_Routines

  LIB$

    LIB$SUB_TIMES

        The Subtract Two Quadword Times routine subtracts two  VMS  internal
        time format times.

           Format:

             LIB$SUB_TIMES  time1 ,time2 ,resultant-time

           Arguments:

        time1

        VMS usage: date_time
        type: quadword (unsigned)
        access: read only
        mechanism: by reference

        First time, from which LIB$SUB_TIMES subtracts the second time.  The
        time1  argument  is  the  address of an unsigned quadword containing
        this number.  Time1 must represent a later time  or  a  longer  time
        interval  than  time2.   Time1  may be either absolute time or delta
        time as long as time2 is of the same type.  If time1 and  time2  are
        of different types, time1 must be the absolute time.

        time2

        VMS usage: date_time
        type: quadword (unsigned)
        access: read only
        mechanism: by reference

        Second time, which LIB$SUB_TIMES subtracts from the first time.  The
        time2  argument  is  the  address of an unsigned quadword containing
        this number.  Time2 must represent an earlier time or a shorter time
        interval  than  time1.   Time2  may be either absolute time or delta
        time as long as time1 is of the same type.  If time2 and  time1  are
        of different types, time2 must be the delta time.

        resultant-time

        VMS usage: date_time
        type: quadword (unsigned)
        access: write only
        mechanism: by reference

        The result of subtracting  time2  from  time1.   The  resultant-time
        argument  is  the  address  of  an  unsigned quadword containing the
        result.   If  both  time1  and   time2   are   delta   times,   then
        resultant-time  is  a  delta  time.   If  both  time1  and time2 are
        absolute times, then resultant-time is a delta time.  If time1 is an
        absolute  time  and time2 is a delta time, then resultant-time is an
        absolute time.


--------------------------------------------------------------------------------
Carl J Lydick | INTERnet: CARL@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL

Disclaimer:  Hey, I understand VAXen and VMS.  That's what I get paid for.  My
understanding of astronomy is purely at the amateur level (or below).  So
unless what I'm saying is directly related to VAX/VMS, don't hold me or my
organization responsible for it.  If it IS related to VAX/VMS, you can try to
hold me responsible for it, but my organization had nothing to do with it.
Newsgroups: comp.os.vms