Supervisor calls 
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 Supervisor calls


>Hi... I'm looking for any information on SVC's, and what they do...
>All I have info on right now, is the SVC 202, (To send a command to
>CMS or CP or whatever...) Does anyone out there have a list of what
>different SVC numbers do? Also, one problem w/ using SVC 202 if you're
>writing something that say uses words greater than 8 bytes, Something like
>if you're writing a prg that sends messages to other users, if you have
>a word that's longer than 8 bytes, the program will chop it up into pieces
>8 bytes each. So, a message Like Hellothere would come out as Hellothe re
>Does anyone know how to transfer something to the system directly, w/o
>having to split it up into doubleword chunks? Any help appreciated...

The function of an SVC is very operating system dependant.  I presume
that since you mention SVC 202, you want info on CMS SVCs.
I am home without my manuals, and I am a bit fuzzy on some of these
but I will do the best I can.  CMS basically has 3 SVCs 202, 203, & 204.
202 is the old style command interface, 203 is mostly used for CMS services,
and is usually the result of a macro expansion.  204 is the new style
command interface.  The primary difference is that 202 uses some 3 byte
address fields, which are a no-no under XA.  204 was introduced in the
CMS 5.5 which is part of VM/XA, but has since been retrofilled into
non XA CMS for compatibility.

As a sop to the great god of compatability,  and to allow the OS compilers
to run under CMS,  a subset of the OS SVCs are also supported.

The 8 byte tokenization problem has been with us as long as CMS has.
There are two ways to get around it.

 1) Use diagnose 8 for CP commands.

            LA   Rx,CMD      CMD contains the CP command.
            LA   Ry,L'CMD    Length of CP command.
            DIAG Rx,Ry,8     Diag is a system macro.
             . . . .
    CMD     DC  C'whatever CP command you want'  Command itself MUST be in caps
    *                                            If MSG, text may be mixed case

    You can also get the CP response back in a buffer in your program.  Uses 2
    more registers and some flag bits in left byte of Rx.  On return, Ry
    contains the CP return code from the command.  (0 = ok)  See the "CP for
    Systems Programming" manual.

 2) Use SVC 202/204 with an "untokenized plist".  I don't remember the details
    offhand, but the manual that describes SVC 202 will show you.  Try the
    CMS command ref or CMS for sysprogs.  Basically, R0 points to a list
    of adcons which point to various parts of the command to be issued,
    and there are some flag bits involved.

Disclaimer: The above writings are the ramblings of one human being
        and have nothing what-so-ever to do with Locus Computing Corp.

Fri, 20 Aug 1993 16:45:23 GMT  
 [ 1 post ] 

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