Darwin - an open source derivative of 4.4BSD (Berkeley Software Distribution Version 4.4) that serves as the core for the Macintosh OS X. There is also a GNU version of Darwin, which is called GNU-Darwin.
Free BSD - the most popular of the BSD operating systems, accounting for approximately 80 percent of BSD installations (at least until Darwin came onto the scene).
MS-DOS - a single-user, single-tasking operating system that uses a command line (i.e., text only) user interface.
Java OS is written primarily in the Java programming language and includes a Java virtual machine (which allows running of any Java program regardless of the type of CPU used) as a fundamental component.
Linux - a high performance, yet completely free, Unix-like operating system launched by Linus Torvalds in 1991.
Solaris was introduced as Sun OS in 1989, and it was based on BSD Unix. TRON (The Real-time Operating system Nucleus) - started by Professor Ken Sakamura of the University of Tokyo in 1984 with the goal of creating an ideal computer architecture.
TRON claims to be the world's most widely used operating system because it is embedded in a vast number and variety of electronic products.
It is possibly the most portable of all operating systems, with the ability to run on more than 50 processors, ranging from the acorn26 to the x86. It is the leading PDA operating system, used in more than 36 million mobile devices, and there are more than 20,000 software titles for it, far more than for any other handheld platform.
Open BSD - spun off from Net BSD in 1996 by Theo de Raadt in Calgary, Alberta because of a desire to place even more emphasis on security. QNX - a Unix-like, POSIX-compliant, real time operating system developed in 1982 that is widely used for mission- and life-critical embedded applications.
AIX (Advanced Interactive e Xecutive) - a proprietary (i.e., commercial) flavor (i.e., variant) of UNIX launched by IBM in 1990 for use on its mainframe computers.
Amiga - launched with the pioneering Amiga personal computer in 1985 and continues to be developed today for the Power PC processor.
HP-UX - a proprietary flavor of UNIX developed by Hewlett-Packard for its HP 9000 series of business servers. IRIX - a proprietary flavor of UNIX introduced by Silicon Graphics, Incorporated (SGI) in 1982 for applications that use three dimensional visualization and virtual reality.
Java OS - developed by Sun Microsystems in 1996 for use in embedded systems (i.e., combinations of circuitry and software built into other products).
Open BSD has a goal of becoming the most secure operating system, and it claims to have had only one remote hole in the default install in more than eight years. QNX can also be used as a desktop operating system and features a unique and attractive GUI.