It’s possible modify the Write Post form?

It’s possible add a code to have personalized Write Post form?
for ex:

Title:
<input type=”text” … />
Article:
<textarea … ></textarea>
New:
<input type=”text” … />
New:
<input type=”text” … />
New:
<input type=”text” … />

all without use the advanced editing function, but modifing the code? what file are need to modify?
Also if the entry in the other input text are copied in the same field of textarea(for ex: with javascript)…

Otherwise exists some plugins for this? or how it’s possible create it(if it’s not possible modify the code of wp)?

thanks all!