Using WordStar v4 on a Kaypro 10 with TurboRom v3.4 and ZCPR33, I
occasionally had a problem of WS not finding its overlay or a
BDOS error on a non-existent drive.
   
The problems occurred when logged on to a different user number
than WS was on (the disk made no difference).  Sometimes there
would not be a problem, and sometimes there was - depending on
which program was run previously (if VEDIT PLUS, WS would NOT
work - if SHOW, WS would work).
  
Upon much investigation, it was found that WS uses memory bytes
02201H and 02202H in some manner to find its overlay and other
things.  BUT these two bytes are not cleared by the WS I have,
but are manipulated in some manner.
  
If memory byte 02201H has the most significant bit set from a
previous program and memory byte 02202H has an acceptable value,
WS will not find its overlay the first time run, but since it
clears that bit when run, it will work fine if run again.
  
If memory byte 02202H has bit 4 set and bit 3 cleared from a
previous program and memory byte 02201H has an acceptable value,
a BDOS error on a non-existent drive occurs.
   
If memory bytes 02201H and 02202H are poked with 0 before running
WS the program appears to work every time.
   
Since WS does start to run, a patch to an internal initialization
routine can also be used to fill the two memory bytes with zeros
either by using WSCHANGE or direct patching.
   
If the user patchable initialization is not being used, run
WSCHANGE, go to selection "E Patching" of the main menu.  Enter
"=" and "INISUB", then enter C3 5B 04.  Return to patch menu
enter "=" and "MORPAT", then enter 21 00 00 22 01 22 C9, and exit
saving patches.
   
That is:
     03BB           INISUB::
     03BB C3 5B 04            JP   045B
  
     045B           MORPAT::
     045B 21 00 00            LD   HL,0
     045E 22 01 22            LD   (02201H),HL
     0461 C9                  RET
  

Originally posted on Lillipute #1 3/5/88 msg #7000 by Ernie Barnhart