Tanenbaum–Torvalds debate mentioned how he developed Linux specifically for the Intel 80386 because it was partly intended as a learning exercise for Torvalds himself; while he conceded that this made the kernel itself less portable than MINIX, he asserted that this was an acceptable design principle, as it made the application programming interface simpler and more portable. For this reason, he stated, "linux is more portable than minix." Following Linus' reply, Tanenbaum argued that the limitations of MINIX relate to him being a professor, stating the requirement for the system to be able to run on the rather limited hardware of the
Linux free software. Work began in 1984. Later, in 1985, Stallman started the Free Software Foundation and wrote the GNU General Public License (GNU GPL) in 1989. By the early 1990s, many of the programs required in an operating system (such as libraries, compilers, text editors, a Unix shell, and a windowing system) were completed, although low-level elements such as device drivers, daemons, and the kernel, called GNU/Hurd, were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time (1991), he would not have decided to write his own. Although not released until