Information Technology Reference
In-Depth Information
hardware, does the web server need to be re-written from scratch, or can it
be written in a hardware-independent fashion? What about the operating
system | does it need to be re-written for every new piece of hardware?
We could go on, but you get the idea. This topic will help you understand
the answers to these questions, and more.
Goals of this chapter
The rest of this chapter discusses three topics in detail:
OS Definition. What is an operating system and what does it do?
OS Challenges. How should we evaluate operating systems, and what
are some of the tradeoffs their designers face?
OS Past, Present and Future. What is the history of operating sys-
tems, and what new functionality are we likely to see in future operating
systems?
1.1
What is an operating system?
An operating system is the layer of software that manages a computer's resources
Denition: operating
system
for its users and their applications. Operating systems run in a wide range of
computer systems. Sometimes they are invisible to the end user, controlling
embedded devices such as toasters, gaming systems, and the many computers
inside modern automobiles and airplanes. Operating systems are also an essen-
tial component of more general-purpose systems such as smartphones, desktop
computers, and servers.
Our discussion will focus on general-purpose operating systems, because the
technologies they need are a superset of the technologies needed for embed-
ded systems. Increasingly though, technologies developed for general-purpose
computing are migrating into the embedded sphere. For example, early mo-
bile phones had simple operating systems to manage the hardware and to run
a handful of primitive applications. Today, smartphones | phones capable of
running independent third party applications | are the fastest growing part
of the mobile phone business. These new devices require much more complete
operating systems, with sophisticated resource management, multi-tasking, se-
curity and failure isolation.
Likewise, automobiles are increasingly software controlled, raising a host of
operating system issues. Can anyone write software for your car? What if
the software fails while you are driving down the highway? How might the
operating system of your car be designed to prevent a computer virus from
