Although LISP and DCL system of the two programs (IntelliCAD & AutoCAD) are highly compatible, there are slight differences. Knowing them before porting may descrease problems considerably.

1) When trying to <b>INSERT</b> a drawing on disk which is defined in the current drawing; "The block 'MYBLOCK' already exists. Do you want to redefine it?" question appears.
AutoCAD does not ask this question, instead, just uses the block defined in the drawing.
e.g. Let current drawing has a pre-defined block named MYBLOCK and let "MYBLOCK.DWG" exists on disk.
When
<font face="Courier New">(command "INSERT" "MYBLOCK.DWG" '(0 0 0) 1 "" "")</font id="Courier New">
is called:
AutoCAD: If drawing does not define MYBLOCK, places DWG file, else places block.
IntelliCAD: If drawing does not define MYBLOCK, places DWG file, else asks to replace whether drawing or block.
Solution: Below code works OK for two programs.

[code](if (tblsearch "BLOCK" "MYBLOK")
(command "INSERT" "MYBLOK" '(0 0 0) 1 "" "")
(command "INSERT" "MYBLOK.DWG" '(0 0 0) 1 "" "")
)[/code]
Alternatively, you can set <b>EXPERT</b> system variable to <b>2</b>

2) At IntelliCAD LISP, if a command is being written in seperate lines, selection set can not lie on a single command line.
e.g.

[code]
;AutoCAD
(defun c:MM ()
(setq set (entlast))
(command "MOVE")
<font color="red">(command set)</font id="red">
<font color="red">(command "")</font id="red">
(command '(10 10 0))
(command ""))

;intelliCAD
(defun c:MM ()
(setq set (entlast))
(command "MOVE")
<font color="green">(command set "")</font id="green">
(command '(10 10 0))
(command ""))
[/code]

3) if <font face="Courier New">(tblnext "block")</font id="Courier New"> process is called after command <font face="Courier New">(command "insert" "*dwgfile" ...)</font id="Courier New"> it will return nil.
Solution:

After
<font face="Courier New">(command "insert" "*dwgfile" ...)</font id="Courier New">
command, call
<font face="Courier New">(tblsearch "block" bnam T)</font id="Courier New">


4) In DCL, <b>client_data_file</b> function which allows user-defined values to dialog box units does not work in IntelliCAD. (<font color="orange">Not tested after version 4</font id="orange">)

5) All options of <b>wcmatch</b> in IntelliCAD may not function as the same as in AutoCAD

6) There can be size differencies in <b>slide_image</b>.

7) In AutoCAD <font face="Courier New">(command "_.STYLE" ....)</font id="Courier New"> automatically enables text mode. In IntelliCAD, it should be used as <font face="Courier New">(command "_.<font color="red">-</font id="red">STYLE" ....)</font id="Courier New">

Entering full names of sub-commands of DIM may be necessary: (<font color="orange">Not tested after version 4</font id="orange">)
[code](command "_.DIM" "<font color="red">_VERTICAL</font id="red">")[/code]


9) There are slight differences in the order of sub options of <b>HATCH</b> command. (<font color="orange">Not tested after version 4</font id="orange">)

10) Do not use command names as LISP variables names. e.g. below line generates an error:

[code](defun c:my_command (/ <font color="red">redraw</font id="red">)
(command "REDRAW")
)[/code]

11) Replace <font color="red">_.OFFSET </font id="red">command with <font color="green">_.PARALLEL</font id="green">, <font color="red">_.PLINE </font id="red">command with <font color="green">_.POLYLINE</font id="green"> for to make sure multi-language programs.

12) In IntelliCAD, selection set string masking only permits * sign. While AutoCAD supports @,#,* etc. Eg:
(ssget "X" '((8 . "WALL*")))