Is there a way we can make a GUI easily, can use arduino mega 2560 to control that GUI.
Like if auduino gets a 5v signal it turns "ON" an led on that GUI and stop watch starts untill arduino stops sending that signal...
There exist many ways to write a PC program with a GUI. Pick a development system for your favourite programming language and start designing the GUI. Then add serial communication (with the Arduino), and add the actions to be taken on the information sent by the Arduino.
i am a beginner, can u tell me software to do that.
i know C language....
Hi,
Try a program called Processing.
It has examples for use with arduino, and there are tutorials and youtube demonstrations.
It uses C+ so you should find it useable.
Tom..... 
This Python GUI demo may be of interest.
Another way to make a GUI is to build a small web application - for example with Python and the Bottle web framework. Personally I find it easier to make a GUI with HTML and CSS than with TKinter or its equivalents.
...R
hi you can also use microsoft visual studio to develop a GUI (windows app C#) that communicates with arduino, and use [using System.IO.Ports] library