MINIX is a family of Unix/POSIX compliant, small, microkernel operating systems (OSs). All versions include source code. MINIX has a strong presence in computer education. MINIX 1 originated to teach college level computer science. MINIX 1 and 2 were used only for education, and by hobbyists. MINIX 1 had a more restrictive license. MINIX 2 and 3 are free, open source, with a BSD-like license. MINIX 3 is the first version intended for more than education. It is optimized for reliability: it is flexible, secure, and self-healing, it keeps running even during software faults; almost everything, including drivers, runs in user space. Over 400 programs are ported to it.