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Apple OS X

Apple inc. USA 2001

under construction





Ten years after the launch of the Mac and the first commercially successful GUI, Apple committed to a radical overhaul of its crown jewels - the Mac's operating system. A few years later and beset by problems, the ill-fated Copland project was cancelled and Apple looked to acquire an OS company to start afresh. After considering deals with Be and Sun, the company announced it would purchase NeXT Computer and its assets and bring Steve Jobs, NeXT's CEO back to the company he founded.

In 2001, seven years after Copland was announced, the next-generation operating system the Mac needed so badly finally arrived - OS X. Based on a version of BSD Unix and featuring an interface that featured transparent windows and animated folder actions, the OS was secure, reliable, easy-to-use and made Windows look dated. Despite being a little rough around the edges and with limited support from third-party applications, the first iteration of the cat-themed operating system won the company a new generation of plaudits and laid the first steps into its evolution of one of the most respected operating systems in modern computing.

Microsoft has taken five years to catch up. The OS X-like Windows Vista is lurching towards a launch date sometime in late 2006. With the move to Intel-powered Macs imminent, those who thought the OS wars were over may be about to proved wrong.


Functions and Structure



interface to the underlying hardware

interface to application programs

interface to the user

interface to the system manager



Resource Allocation.






IO devices.

Support Services. Another important operating system task is providing support services for processes. These include:

Support for IO operations. We've already discussed how the operating system controls IO to enforce a protection scheme.

File system management.



Interrupts and Traps.


Operating System Design Principles





Backwards compatibility and emulation

Layered design

Distinction between mechanisms and policies:

a mechanism is a facility the system provides the system manager. For example, VMS allows the manager to control whether or not a given account can be logged in to over a network connection.

a policy is a decision made by the manager(s) about how to accomplish some goal. For example, a company may decide that it will not allow privileged accounts to be logged in to over a network connection.

mechanisms are the tools used to implement policies.

Virtual Machines

The concept of virtual machines is closely related to layering.


Common features





Go Backto software main pageGo to main pagesearch Last Updated on 8 December, 2005 For suggestions please mail the editors 

Footnotes & References