The Modern Era
Beyond the minicomputer came a new type of machine, cheaper, faster,
and for the masses: the personal computer, or PC as we call it today. Led
by Apple’s early machines (e.g., the Apple II) and the IBM PC, this new
breed of machine would soon become the dominant force in computing,
as their low-cost enabled one machine per desktop instead of a shared
minicomputer per workgroup.
Unfortunately, for operating systems, the PC at first represented a
great leap backwards, as early systems forgot (or never knew of) the
lessons learned in the era of minicomputers. For example, early operating
systems such as DOS (the Disk Operating System, from Microsoft)
didn’t think memory protection was important; thus, a malicious (or perhaps
just a poorly-programmed) application could scribble all overmemory.
The first generations of the Mac OS (v9 and earlier) took a cooperative
approach to job scheduling; thus, a thread that accidentally got stuck
in an infinite loop could take over the entire system, forcing a reboot. The
painful list of OS features missing in this generation of systems is long,
too long for a full discussion here.
Fortunately, after some years of suffering, the old features ofminicomputer
operating systems started to find their way onto the desktop. For
example, Mac OS X has UNIX at its core, including all of the features
one would expect from such a mature system. Windows has similarly
adopted many of the great ideas in computing history, starting in particular
with Windows NT, a great leap forward in Microsoft OS technology.
Even today’s cell phones run operating systems (such as Linux) that are
much more like what a minicomputer ran in the 1970s than what a PC