Definizione di GNU
GNU is an operating system completely free, created in 1984 by Richard Stallman and based on Unix (the most spread operating system in the mini-computer world, belonging from 1979 to the telephone colossus AT&T - American Telephone and Telegraph, Inc). Richard Stallman baptized this operating system with the GNU acronym, as "GNU is not Unix", a definition formulated according to an ancient hacker community custom. In other terms: GNU is not the AT&T Unix, it is not therefore proprietary, but it has the same functionalities and it is compatible with it. So, unlike Unix, GNU would have been free, everyone could have access to its source code.