Is it possible to program Android to act as physical USB keyboard?

What I really want to know is whether it is a hardware problem, or a software problem. Could I plug my android phone into a computer via USB and have it act as a hardware keyboard. I do not want to install anything on the computer, I want android to behave like the standard hardware.

Edit: Clarification I want to write a program/library for android that enables the device to fully emulate an ordinary keyboard, so that the operating system reports it as a standard keyboard device, and it would work in the BIOS or anywhere else that a keyboard works.