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Undocumented System Variables

Variable Type Range Introduced Notes
_LINFO string - pre R12 Hardware lock serial number; responds to (getvar "_LINFO") only.
_PKSER string - R9[2] The AutoCAD serial number (read-only).
Note that in versions of AutoCAD prior to R11(?), the serial number was a string in the executable which could be hacked to read 00-000000. In R11(?) a hook into the ZOOM command was enabled to immediately crash AutoCAD if the serial number string was tampered with.[2]
_SERVER boolean 0/1 R11[2] Network license server status (read-only).
_VERNUM string - R13 AutoCAD build number.
AUXSTAT integer -32768 - 32767 R13 auxiliary input device status[3]
AXISMODE boolean 0/1 pre R12 Holdover from old AXIS command; no longer used.
AXISUNIT '(x y) - pre R12 Holdover from old AXIS command; no longer used.
BS_BITS[2] integer -32768 - 32767 R11 only  
DBGLISTALL * * R10[2] Unknown function.
*Note that this was an integer with range -32768 - 32767 from R10 - R11, then it became a boolean (0/1).[2]
ENTEXTS integer [0, 1, 2] R12 Controls drawing extents calculation.
0 : extents are calculated each time they're needed (slower, but uses less memory).
1 : cache extents of each entity in short (2-byte) values if possible (compromise between speed and memory efficiency).
2 : cache extents of each entity as long (4-byte) values (fastest extents calculations, but uses more storage memory).
ENTMODS integer 0 - ~4Gig R12 Increments every time a database object is modified (read-only).
FORCE_PAGING integer 0 - ~4Gig R13  
GLOBCHECK integer [0, 1, 2, 3] R13 3 : show DCL dialog size when displaying dialog.
>0 : disallow local-language commands (very useful for developers!).
JWDEBUG[2] ? ? R9 - R10 Probably a "debug" flag used by a programmer with initials J.W. (John Walker?)
KESDEBUG[2] ? ? R9 only Probably a "debug" flag used by a programmer with initials K.E.S.
LAZYLOAD boolean 0/1 R13  
NODENAME string - R13 AutoCAD node name.
NOMUTT boolean 0/1 R14.01 1 (True) : No input prompts are displayed.
PHANDLE integer 0 - ~4Gig R12  
PRODUCT string - R14 Product name (e.g. "AutoCAD") (read-only).
PROGRAM string - R14 Executable name (e.g. "acad") (read-only).
QAFLAGS bitcode 0 - 32767* R11 bit 0 (1) : ^C in menu macro cancels grips (acts like keyboard <Esc>).
bit 1 (2) : no pause during text screen listings.
bit 2 (4) : no "alert" dialogs (text display instead).
bit 7 (128) : accepts "screen picks" (point lists) via (command) function.
*Note that this was an integer with range -32768 - 32767 in R11, then it changed to 0 - 32767 in R12.[2]

Additional Information:

  1. Undocumented system variables are sometimes named internally with an asterisk preceding their name. The asterisk may be included when retrieving such system variables via AutoLISP. For example, (getvar "_PKSER")  and  (getvar "*_PKSER") both return the serial number.[2]
  2. Prior to R12, AUPREC and LUPREC accepted integers in the range 0 - 18. Beginning with R12, these two system variables no longer accept values larger than 8. If you save an R11 drawing with LUPREC or AUPREC values higher than 8, they are honored in R12 and later -- however, once you change them they cannot be changed back (except via UNDO).[2]
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