how can i produce a digital notepad?

Question

hi
i want try to produce a digital notepad in my company and i want produce it myself... because i want have a market for my product.
how can i start?
what hardware i need?
what programming?

i want save every text that write on screen with a pen... every thing like text, image or every handwriting.
first i need know how i produce hardware ? a memory, a cpu??!! and a touch screen
whether i must buy that and create a circuit?

please help me
thanks alot