os-java:Introduction

An operating system is a program that manages the computer hardware.

Operating systems for hand-held computers are designed to provide an
environment in which a user can easily interface with the computer to execute programs.

Mainframe operating systems are designed primarily to optimize utilization of hardware.

Personal computer (PC) operating systems support complex games, business applications, and everything in between.

some operating systems are designed to be convenient, others to be efficient, and others some combination of the two.


Abstract view of the components of a computer system.

(Figure 1.1)

The hardware

• the central processing unit (CPU), the memory, and the input/output (I/O) devices
• provides the basic computing resources for the system.

The application programs

• such as word processors, spreadsheets, compilers, and web browsers

• define the ways in which these resources are used to solve users'computing problems.

The operating system controls and coordinates the use of the hardware among the various application programs for the various users.

An operating system is similar to a government.Like a government, it performs no useful function by itself. It simply provides an environment within which other programs can do useful work.

pc

• In this case, the operating system is designed mostly for ease of use.
• with some attention paid to performance and none paid to resource utilization.
  

mainframe or minicomputer

• users are accessing the same computer through other terminals.
• The operating system in such cases is designed to maximize resource utilization.
• To assure that all available CPU time, memory, and I/O are used efficiently and that no individual user takes more than her fair share.

workstations

• users sit at workstations connected to networks of other workstations and servers.
• These users have dedicated resources at their disposal, but they also share resources such as networking and servers—file, compute and print servers.
• Therefore, their operating system is designed to compromise between individual usability and resource utilization.
  

handheld

• These devices are mostly standalone units used singly by individual users.
  
• Because of power and interface limitations, they perform relatively few remote operations.
• performance per amount of battery life is important as well.
  

embedded

• May have numeric keypads and may turn indicator lights on or off to show status.
• But mostly they and their operating systems are designed to run without user intervention.