Page 28 - DCAP103_Principle of operating system

Unit 1: Operating System

• Security flaws: Some software errors leave a door open for the system to be broken into Notes
by unauthorized intruders. As these flaws are discovered, unauthorized intruders may
try to use these to gain illegal access to your system. Patching these flaws often will help
keep your computer system secure. How this is done will be explained later.
• Sometimes errors in the operating system will cause the computer not to work correctly
with some peripheral devices such as printers.

Giving sound command make sure sound card is enabled.

1.7.5 Types of Operating System

Within the broad family of operating systems, there are generally four types, categorized based
on the types of computers they control and the sort of applications they support. The categories
are real-time operating system, single user single task, single user multitasking and multi-user.
1.7.5.1 Real-Time Operating System (RTOS)

Real-time operating systems are used to control machinery, scientific instruments and industrial
systems such as embedded systems (programmable thermostats, household appliance controllers),
industrial robots, spacecraft, industrial control (manufacturing, production, power generation,
fabrication, and refining), and scientific research equipment.

An RTOS typically has very little user-interface capability, and no end-user utilities, since the
system will be a “sealed box” when delivered for use. A very important part of an RTOS is
managing the resources of the computer so that a particular operation executes in precisely the
same amount of time, every time it occurs. In a complex machine, having a part move more
quickly just because system resources are available may be just as catastrophic as having it not
move at all because the system is busy.
An RTOS facilitates the creation of a real-time system, but does not guarantee the final result will
be real-time; this requires correct development of the software. An RTOS does not necessarily
have high throughput; rather, an RTOS provides facilities which, if used properly, guarantee
deadlines can be met generally (soft real-time) or deterministically (hard real-time). An RTOS
will typically use specialized scheduling algorithms in order to provide the real-time developer
with the tools necessary to produce deterministic behavior in the final system. An RTOS is
valued more for how quickly and/or predictably it can respond to a particular event than for
the given amount of work it can perform over time. Key factors in an RTOS are therefore a
minimal interrupt latency (the time between the generation of an interrupt by a device and the
servicing of the device which generated the interrupt) and a minimal thread switching latency
(the time needed by the operating system to switch the CPU to another thread).
An early example of a large-scale real-time operating system was Transaction Processing Facility.
Current users include Sabre (reservations), Amadeus (reservations), VISA Inc (authorizations),
Holiday Inn (central reservations), CBOE (order routing), Singapore Airlines, KLM, Qantas,
Amtrak, Marriott International , Worldspan and the NYPD (911 system).
1.7.5.2 Single User, Single Task

As the name implies, this operating system is designed to manage the computer so that one
user can effectively do one thing at a time. The Palm OS for Palm handheld computers is a good
example of a modern single-user, single-task operating system.

LOVELY PROFESSIONAL UNIVERSITY 21