Information Technology Reference
In-Depth Information
to designate which application we wish to run. The operating sys
tem then locates the relevant programs and data for that application
and provides the program with a way to display information in win
dows. If we subsequently run a second application, then the operat
ing system keeps track of both programs and their data. For exam
ple, the operating system allocates some virtual memory to each
application, determines which parts of that material should be
loaded into main memory, and schedules work so that progress can
be made on both applications. Similarly, if we use the mouse to click
on one application and then on the other, the operating system
keeps track of which program to highlight at each moment. If we
type data, the operating system decides which program should re
ceive the data we provide.
Similarly, if we tell one program to print results, then the oper
ating system interacts with the printer and coordinates the printing
together with the currently running applications. Of course, specific
functions of our applications are handled by those individual pro
grams, but the operating system helps provide coordination and
handles various behindthescenes tasks.
The list of tasks handled by an operating system is reasonably
long, so it is hardly surprising to learn that these tasks can be done
in more than one way. As an analogy, consider the choices we have
in purchasing a car. If our goal is to move a family with several chil
dren and their belongings, we might purchase a minivan. If our goal
is speed—with the need for few passengers—we might consider a
sports car. If our goal is economy, we might want a compact car
with high gas mileage. If we want to consume a lot of gas and hog
the road, we might buy an SUV. Each of these vehicles meets basic
transportation goals, but different types of cars reflect different pri
orities and perspectives.
The development of operating systems similarly reflects differ
ent approaches to the coordination and streamlining of computer
tasks. For example, the first versions of Unix (from which the Linux
operating system developed) were designed at Bell Laboratories, the
primary research organization of AT&T, to assist researchers in
their work. The idea was to provide a common environment for
