Changing in and out of ( SYSTEM mode

[John Woods]

I have a C application running in user mode that I would like to have call 
an assembler subroutine that currently uses the (good old) BALR interface 
to VCADTLKP to see if a disk mode is accessed... I know, I know... but hey, 
the code works and it does what I want.  The only problem, of course, is 
that the C code is running is user mode and the assembler code would really 
like to be in "( SYSTEM" mode.  It's been a long time since I wrote a lot 
of CMS code, but I seem to remember that there was a reasonably easy way to 
flip in and out of SYSTEM mode (I think I need storage key zero as 
well).  I know I could restruture everything, but I'm trying to avoid that 
if possible.  A few lines of assembler would certainly be easier than 
changing a few lines of C because the C application is shared between a 
number of different people... weanies, actually.  ;-)

Thanks
John