Batch Calculator

Open Notepad
Copy the following and paste it:

@echo off
title Calculator By Subash
:back
echo
echo-----------------------------------------------------------------------------
echo Welcome to Calculator by Subash Basnet.
echo-----------------------------------------------------------------------------
echo.
set /p sum=
set /a ans = %sum%
echo.
echo = %ans%
echo----------------------------------------------------------------------------
pause
cls
echo.
echo ----------------------------------------------------------------------------
echo previous answer: %ans%
echo ----------------------------------------------------------------------------
goto back
exit

Now save it with extension .bat for eg : calculator.bat
Open it and enjoy