Algorithme en Batch

Set /p "string=Entrez un..NimporteQuoi  "
If defined string (
     Echo 1 >test.txt )
 )

Set /a variable=%nb1%%OP%%nb2%

@echo off 
cls
echo.
echo -  soustraction 
echo *  multipliquation 
echo /  division 
echo +  adition 

setlocal 

:debut 
echo.
set /p cmdresult=Operation : 

if "%cmdresult:~0,1%"=="q" ( goto :eof 
) 
if "%cmdresult:~0,1%"=="h" ( 
   call hex %cmdresult:~1% >nul 
   goto display 
) 
set /a result=%cmdresult% 

:display 
echo =%result% 
echo. 
goto debut

:eof
exit