; The following program is sample output from the LISP Generator (more info at www.LispGen.com). 
; The LISP Generator is a full-featured code generator for Autocad's AuotLISP language.
; Legal notices:
; - This sample program is intended as a demonstration only.
; - The program is available on an 'as-is' basis with no warranties, either expressed or implied, of any kind.
; - The program may only be used at the user's own risk.
; - No license or rights to the code are either given or forfeited.
; Everything that follows is direct and unaltered output from the LISP Generator.

; This program was created on December 8 2006 using the LISP Generator.

; Define the function (the program). 
(defun c:INCH-CM ( / ENT OLDTEXT INCHES CMS CM-STR NEWTEXT OLDCE OLDERR OLDTE)
  ; Save the current value of cmdecho then redefine it. 
  (setq OLDCE (getvar "cmdecho"))
  (setvar "cmdecho" 1)
  ; Save the current value of texteval then set it to 1
  (setq OLDTE (getvar "texteval"))
  (setvar "texteval" 1)
  ; Save the current value of the error handling subroutine then redefine it. 
  (setq OLDERR *error*)
  (defun *error* (errmes)
    (princ (strcat "\nExecution of INCH-CM halted by the following error: " ERRMES))
    (setvar "cmdecho" OLDCE)
    (setq *error* OLDERR)
    (prin1)
  )
  ;(setq *error* nil)
  ; NOTE: to turn error handling off, erase the semicolon in the line above. 

  ; GET a ENTITY from the user and store it in ENT. 
  (setq ENT (car (entsel "\nSelect object to modify: ")))

  ; EXTRACT the Text string from the entity ENT and store it in OLDTEXT.
  (setq OLDTEXT (cdr (assoc 1 (entget ENT)))) 

  ; CONVERT the string OLDTEXT to a real number and store it in INCHES
  (setq INCHES (atof OLDTEXT))

  ; assign result of MATH calculation to CMS. 
  (setq CMS (* INCHES 2.54))

  ; CONVERT the real number CMS to a string and store it in CM-STR
  (setq CM-STR (rtos CMS 2 2))

  ; OPERATION - store the result in NEWTEXT.  
  (setq NEWTEXT (STRCAT OLDTEXT " {" CM-STR " cm}"))

  ; MODIFY the code 1 value (Text string)  of the entity ENT. 
  (if (assoc 1 (entget ENT))
    (entmod (subst (cons 1 NEWTEXT) (assoc 1 (entget ENT)) (entget ENT)))
    (entmod (cons (cons 1 NEWTEXT) (entget ENT)))
  )

  ; Reset "cmdecho" to previous value. 
  (setvar "cmdecho" OLDCE)
  ; Reset "texteval" to previous value. 
  (setvar "texteval" OLDTE)
  ; Reset *error* to previous definition. 
  (setq *error* OLDERR)
  ; Exit quietly (no return value.)
  (prin1)
)