SD-4.3 - 06 feb 1982
                  R.B. Strand

SD-4.x  uses the questionable method of modifying the trap  table 
in BDOS to disable the normal BDOS error messages.   This  allows 
the  identification  of  invalid  drives and  bad  disks  by  SD.  
However,  earlier  versions  did this modifying  without  testing 
whether  or not the vector pointer at BASE+5 was virgin,  or  had 
been  changed by DDT,  UNSPOOL or the like.   This created  great 
confusion (and system crashes).  To alleviate the problem, SD now 
checks  whether the pointer is valid (L-reg = 6) before  swapping 
the BDOS trap vectors, and also only swaps them when the all-disk 
search option is requested ($D).

Additional  changes  include the addition of  dim  (vs.  reverse) 
characters  for  the ADM-31 and similar CRTs.   These are  merely 
substituted for the reverse characters.   Also,  when using RMAC, 
there is no requirement for external defs of BASE, etc.  Instead, 
merely  add an ASEG statement and compile as if  with  MAC.   MAC 
users  should  ignore  the  "B" error flag  for  this  statement.  
Flipping  on  the  RMAC  flag  now  still  requires  linking  the 
externals.

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