Java Reference
In-Depth Information
1.4.3 Scheduling Operations
The OS is responsible for scheduling programs' activities to make efficient use of system
resources. Many of today's operating systems support such techniques as
multiprogramming
,
multithreading
, and
multiprocessing
to increase system performance.
Multiprogramming
allows multiple programs to run simultaneously by sharing the same
CPU. The CPU is much faster than the computer's other components. As a result, it is idle
most of the time—for example, while waiting for data to be transferred from a disk or waiting
for other system resources to respond. A multiprogramming OS takes advantage of this situa-
tion by allowing multiple programs to use the CPU when it would otherwise be idle. For
example, multiprogramming enables you to use a word processor to edit a file at the same
time as your Web browser is downloading a file.
Multithreading
allows a single program to execute multiple tasks at the same time. For
instance, a word-processing program allows users to simultaneously edit text and save it to a
disk. In this example, editing and saving are two tasks within the same application. These two
tasks may run concurrently.
Multiprocessing
, or
parallel processing
, uses two or more processors together to per-
form subtasks concurrently and then combine solutions of the subtasks to obtain a solution
for the entire task. It is like a surgical operation where several doctors work together on one
patient.
multiprogramming
multithreading
multiprocessing
1.18
What is an operating system? List some popular operating systems.
✓
✓
Check
1.19
What are the major responsibilities of an operating system?
Point
1.20
What are multiprogramming, multithreading, and multiprocessing?
Java is a powerful and versatile programming language for developing software
running on mobile devices, desktop computers, and servers.
Key
Point
This topic introduces Java programming. Java was developed by a team led by James Gosling
at Sun Microsystems. Sun Microsystems was purchased by Oracle in 2010. Originally called
Oak,
Java was designed in 1991 for use in embedded chips in consumer electronic appliances.
In 1995, renamed
Java
, it was redesigned for developing Web applications. For the history of
Java has become enormously popular. Its rapid rise and wide acceptance can be traced to
its design characteristics, particularly its promise that you can write a program once and run
it anywhere. As stated by its designer, Java is
simple
,
object oriented
,
distributed
,
interpreted
,
robust
,
secure
,
architecture neutral
,
portable
,
high performance
,
multithreaded
,
and
dynamic.
For the anatomy of Java characteristics, see
www.cs.armstrong.edu/liang/
Java is a full-featured, general-purpose programming language that can be used to develop
robust mission-critical applications. Today, it is employed not only for Web programming, but
also for developing standalone applications across platforms on servers, desktop computers,
and mobile devices. It was used to develop the code to communicate with and control the
robotic rover on Mars. Many companies that once considered Java to be more hype than sub-
stance are now using it to create distributed applications accessed by customers and partners
across the Internet. For every new project being developed today, companies are asking how
they can use Java to make their work easier.
The World Wide Web is an electronic information repository that can be accessed on the
Internet from anywhere in the world. The Internet, the Web's infrastructure, has been around
for more than forty years. The colorful World Wide Web and sophisticated Web browsers are
the major reason for the Internet's popularity.
