Microsoft's Windows series of operating systems, which currently dominate the computer industry, have a long and colorful history. Microsoft gained prominence with its first operating system, DOS ("disk operating system"), which was a text-based system. If you wanted to run a program, you typed the name of the program at the "command line" and DOS would run it for you.
If you wanted to delete a file, you typed "del" and the name of the file to delete it. Although primitive by today's standards, DOS was the provided operating system for the original IBM PC, and when the latter began selling in huge numbers, it established Microsoft's position. The first release of Windows, in 1985, can be seen as a reaction to the introduction of the Apple Macintosh the year before.
The first Windows was not a whole operating system so much as just a shell that provided a graphical interface, a mouse-based way to run programs while DOS, behind the scenes, still did all the work. While this first version contained many of the features taken for granted now, it had a long way to go. For example, multiple programs could be running in separate windows, but the windows could not overlap.
Another problem with early versions of Windows was the use of nonpreemptive multitasking, which means the applications were responsible for giving up the CPU when their time slice was over. In contrast, most operating systems, including current versions of Windows, use preemptive multitasking, in which the CPU control automatically returns to the operating system after an application's time is up.
With nonpreemptive multitasking, an application is expected to "check in" with the operating system every so often, so the operating system can regain control. The problem arises when the program "crashes" or is tied up waiting for some event that isn't occurring. If the application never checks in, the operating system never gets control back, and the whole system is frozen. With preemptive multitasking, a misbehaving application won't keep the operating system from maintaining control of the computer. Other applications are allowed to continue.
Windows really took off with the release of Windows 95. This version was the first that did not need DOS to be installed on the computer first. Parallel with the development of Windows 95, however, Microsoft had developed a completely new operating system, called NT, for "new technology." Originally, NT was supposed to have been a text-based operating system like DOS, but during development, Microsoft decided it would have a graphical interface and be released under the name Windows NT.
Now, Microsoft had two diverging operating systems: Windows 95, an evolutionary development from the days of DOS, and Windows NT, a new operating system with a more modern design and all the interface features of Windows. Microsoft developed both because of backwards compatibility. Just like Intel and their CPU development, Microsoft worried about forcing everyone to switch to a completely new operating system.
Although Microsoft took pains to allow older software and hardware to work with NT, the system was so different that some incompatibility was inevitable. Thus, Microsoft hedged its bets and kept the old operating system alive, reasoning that home users would use Windows 95 and business users would switch to Windows NT.
Eventually, though, the "new technology" won. Windows 95 became Windows 98 and then Windows ME ("millennium edition"). Windows NT became Windows 2000 and then Windows XP. With Windows XP, Microsoft is only producing a single operating system again. Windows XP is used by home and business users alike.
The UNIX operating system, developed at AT&T's Bell Laboratories, has been around for over thirty years. Where operating systems like Windows tend to emphasize features that help novice users, UNIX emphasizes features that help programmers and expert users. For example, UNIX has a feature called a pipe, which is a mechanism for setting the output of one program as the input of another program.
If Program A corrects the spelling of a text document, Program B formats a document in a three-column layout, and Program C prints a document, then a user can pass a document through A and B to C to spell-check, format, and print the document in a single command.
Though UNIX is old, it has all the features of a modern operating system, including multitasking. One of its strengths is its simplicity, which allows it to be easily modified for use on newer computers.
By itself, though, UNIX has no graphical interface; it is purely a text-based operating system. This problem is quickly remedied through the use of X-Windows, a separate graphical user interface system that runs on top of UNIX. Although UNIX and X-Windows are two different things, and X-Windows could be run on other operating systems, X-Windows can be considered the de facto interface for UNIX, except on the Macintosh. UNIX has surged in popularity in the last few years because of Linux.
UNIX offers users a great deal of low-level control and is therefore popular with expert users. Home users, though, have been slower to accept this operating system. Many popular programs are not available for UNIX, and it is more difficult for the typical home user to learn. Some UNIX programmers almost seem to take pride in offering obscure commands and interfaces.
Mac OS is the operating system for the Apple Macintosh computer; the OS stands for "operating system." Unlike UNIX, the Mac OS developers strove to make their operating system as painless to use as possible. Many of the features that are common to all graphical interfaces were introduced in Mac OS.
The first versions of Mac OS, simply called "System," as in "System 1.0," only supported a black-and-white display and could only run a single program at a time. However, users could switch from one program to another, giving the appearance of multitasking. By version 8.0, the name changed to Mac OS and the operating system supported multitasking, albeit nonpreemptive multitasking.
A current version is Mac OS X, where the X indicates the roman number for 10. This version actually uses Unix as the base operating system, while providing a polished graphical interface (called "Aqua") that is as easy to use as Macintosh owners expect. While the Mac OS holds only a tiny percentage of the marketplace, those who use the Macintosh are a devoted bunch, almost fanatical in their appreciation of the operating system's elegance.
The operating systems are designed for use on personal or larger computers. The Palm OS operating system is for small computers. It was designed for the Palm Pilot, one of the original personal digital assistants. A PDA, as it's called, is a handheld computer that functions as an appointment calendar, note pad, and calculator, and can perform other basic computing tasks.
Over time, PDAs and cell phones have merged, creating "smart phones" with e-mail and Web browsing capability in addition to basic PDA and cell phone features. The Palm OS is a tiny operating system compared to the other systems, because the storage capabilities of handheld devices are so small. This small storage space is not a problem because Palm OS only needs to support a fraction of the features of the others. It doesn't need complicated file management, for example.
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