I am a student, 17 years of age and wanting to access all of my files at greatest ease. i would like to have a system like this:

Computer A, B and C are the computers on which I work and to which the files should be available. Server A is located in my room and I can install Ubuntu on it.

What is the goal? I want to edit files on computer A (e.g.) and computer A should update the file on my server, afterwards the server should update the files on computer B and C. (The same goes for editing files on computer B, afterwards the server has to update the files on A and C.)

How am I able to set-up a network like this? It is about music, movies, pictures, documents...

Thanks for those who are going to reply!