Hi Amardeep,I agree with Joseph. Please Go to below link for "why startup code is required" in Detail?http://www.keil.com/support/man/docs/gsac/...tupCodeARM7.htmAlso I am attaching one pdf document. My Experience with Working with Keil uVision4Hope it helps you...--Gurpreet SinghIMBUENT TECHNOLOGIES PVT.LTD.(INDIA)" A person who never make mistakes,never try new things"