Hello Barry,
 
 BB> ...the stack is the same on return from Int 2E.
 
 DB> It's not the same on the return.
 DB> SS:SP are toasted after the INT 2E call.
 
 DB> BEFORE INT 2E CALL
 DB> SS = 1538 SP = FFFE
 
 DB> AFTER INT 2E CALL
 DB> SS = 0E38 SP = 0603
 
 DB> Which is why...SS:SP...needs to be saved.
 BB> I reassembled with the 2 relevant lines rem'ed out.
 BB> My OS is ms-dos 6.20 rev. A
 The above test was with MS-DOS v6.20 rev A too.
 BB> I tried to use the debug.exe that came with dos 6.20, but the tsr
 Here's my "test" that I used with DOS's debug program:
=] INT2ETST.DBG [==========================================================
A
mov     BX,200      ;need to adjust memory size freeing some for COMMAND.COM
mov     CL,4        ;otherwise you'll get a memory error with COMMAND.COM 
shr     BX,CL
inc     BX
mov     AH,4A
int     21
mov     SI,80
int     2E
NINT2ETST.COM
RCX
200
W
Q
===========================================================================
 Snip 'N' save the test to the indicated file above. Then use
 DEBUG < INT2ETST.DBG to create the COM file.
 Now from the command line, try this:
 DEBUG INT2ETST.COM VER
 Then (P)roceed step through the code, you'll notice that after the INT 2E
 call EVERYthing except CS:IP is destroyed. (with my DOS it is)
 When I say EVERYthing, I mean it, I just noticed some extras ones being
 destroyed. Here's a run down of my findings for the individual registers.
 AX - destroyed     CS - preserved      BP - destroyed      SI - destroyed
 BX - destroyed     DS - destroyed      IP - ---------      DI - destroyed
 CX - destroyed     ES - destroyed      SP - destroyed
 DX - destroyed     SS - destroyed                       flags - destroyed
 "destroyed" means the original value before the call was modified in some
 way. "preserved" means the original value maintained itself during the call.
 The important ones here would be: SS:SP, DS and the flags, the rest can
 probably be junked as is.
 Cheers,
  
... Documentation - The worst part of programming.    
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