How to read disks?

In programming how do you go about reading raw data off of disks. Note: not with a hex-editor, I know how to do that. I basically want to make my own tool.

For example; I want to be able to read the raw data off of a flash drive or some other disk so I can find deleted data. Is it as simple as opening a file and reading a stream? Can someone point me in the right directio开发者_运维百科n?

Obviously I would want the data to appear in hex so that I can scan for file signatures (http://www.garykessler.net/library/file_sigs.html)

C and Python are the ones I am really curious about. Will the standard libraries allow you to open a disk and read data from it directly?

Linux and Windows are two OS's I use.

Thanks