Conclusion

Microcomputer operating systems are only about 25 years old, and evolution has been rapid. Within about ten years, this category of OS had transitioned from 8-bit to 16-bit code, and was on its way to being the first type of computer to employ a graphical user interface. Indeed, by the time they were only about 15 years old, microcomputer OSs had acquired most of the characteristics of their mainframe parents, including such things as virtual memory, true multitasking, and the use of 32-bit code. Of course, much of this development was made possible by the rapid improvements in hardware. The original MS-DOS had to work with a computer whose CPU ran at under 5 MHz and which had access to only 64 Kb of memory. Today's Windows 2000 can expect to luxuriate in a machine with an 800 MHz CPU and 128 MB or more of memory. Generally speaking, progress in the OS, and necessarily, therefore, improvements in application software that depends on the OS, have significantly lagged that of hardware. For example, Intel had a true 32-bit CPU (the 80386) in 1985, but Microsoft's mainstream 32-bit OS, Windows 95, didn't appear until ten years later. These delays are partly attributable to the need to accommodate legacy software, and partly to the demands that graphical UIs and the increasing proliferation of peripheral devices have made on programmers.

The next stage of evolution in desktop OSs will be to the microkernel-kernel-shell architecture pioneered by Unix. This will make possible significantly more stable software, and will more easily accommodate the streaming media applications that are appearing with the increased integration of digital video and sound in computer programs. Windows 2000 has already evolved in this way, and the Mac OS should follow soon. Unix and Linux, which are now not all that different from regular desktop OSs, have of course implemented this approach as well. It seems likely that Microsoft will now quickly move away from the Windows 95–98 OS family in favor of a lighter weight version of Windows 2000. On the other hand, the bigger is better phenomenon has its limits. While 64-bit versions of most types of Unix/Linux are already widely available, and an equivalent for Windows 2000 should follow soon, itseems probable that these OSs will remain in the server environment for some time to come.

Although Microsoft's dominance of the desktop OS market seems to be unchallenged (barring some radical settlement of the Justice Department's suit), the desktop space is not where the growth is. The rapidly expanding market now is for smaller and simpler devices, such as cell phones and palmtops on the low end and set-top boxes and "information appliances" (see Chapter 12) on the high end. These devices will employ a much lighter OS than that now used on the desktop. The general idea is that instead of using local OS services, these intrinsically networked machines will get much of their operating and application capabilities from servers on the Internet. We'll turn to this concept in detail in Chapter 12, but before studying these concepts, it's essential to complete our survey of software. Next up is a description of programming languages.