Transcript Operating Systems

Operating Systems
Contents
What is an Operating System?
Operating System Evaluation
Operating System Design
Some new components in the Operating
Systems
Operating Systems
What is a house?
The house is a dwelling
place which enables
people to use various
facilities in comfort
A house gives consistent
services and interfaces,
e.g. switches, taps,
sockets, aerial leads,
doors, windows...
People
(service users)
House
Hardware
(e.g. power stations,
satellites, water mains)
Operating Systems
What is an OS?
The OS is a software
system which sits between
the hardware and the
application software
An OS give consistent
services and interfaces,
e.g. disc access, keyboard
input, video output,
memory management...
Application Software
Operating System
Hardware
Operating Systems
Computing without an OS
It is possible to ignore the OS and take over the
hardware directly
But software that does this is
making life difficult for itself
probably implementing its own internal OS anyway
usually a game system which does not need a complex,
full-featured OS to work
Modern PC software uses the OS
Operating Systems
Computing with an OS
Share the “processor power”…
 Share Resources
 E.g. Keep track of used and unused memory and drive space,
arbitrate between demands on scarce resources
 Multitasking
 Run multiple programs in their own space, sharing resources
 Networking
 Communicate between computers even they have different
hardware and software – standardised data formats
 OS often comes with a GUI – may be many choices of GUI
Operating Systems
Examples
 Big Computers
 Bespoke versions of Linux e.g. CLE for HECToR (a UK National
Supercomputing Service resource - http://www.hector.ac.uk/)
 Servers
 Windows Server, MacOS, Linux – many versions of each
 Desk top computers
 Windows (based on Windows NT)
 MacOS (built on top of Unix)
 Linux (many varieties, many GUIs)
 Portable devices
 Android (built on Linux), Windows Mobile 8, IOS (built on Unix), Blackberry
(based on QNX)
Operating Systems
Operating System Evolution
 The first computers
had
 small quantities of
memory
 limited processing
abilities
 a highly restrictive
interface (keyboard
only)
 and monochrome
displays
Operating Systems
Operating System Evolution
To control the hardware and perform useful tasks,
simple instructions had to be given
These instructions took the form of typed
sequences of commands
This was the birth of the command-line interface
(the CLI)
An early but powerful version was UNIX (also
available in a slightly different form as Linux for
modern PCs)
Operating Systems
Loading the OS - BIOS v UEFI
 EFI (now UEFI) is a secure boot loader
system that replaces the old BIOS
approach
 Checks the NVRAM custom settings
 Loads only the signed interrupt handlers
and device drivers
 Initializes registers and power management
 Performs the power-on self-test (POST)
 Displays system settings
 Determines which devices are bootable
 Initiates the signed OS start-up sequence
Operating Systems
Operating System Evolution - GUIs
 Most people are used to
using a GUI (Graphical
User Interface) to control a
computer
 The GUI was invented in
the early 1970’s at Xerox
PARC (Palo Alto Research
Center)
 Modern GUIs are derived
from this first GUI
A screen grab from Windows 3.1
Operating Systems
Operating System Design
The design of the operating system may be very
closely tied to the hardware platform that it is to be
run on
Example: Older Blackberry & Nokia phone software
It is possible to have a “hardware abstraction
layer” to reduce the hardware-specific nature of an
OS
Example: Device drivers for Windows
Look up “monolithic” and “micro-kernel” OSes
Operating Systems
Desktop Windows Manager
Their drawing is
redirected to off-screen
surfaces in video memory,
which are then rendered
into a desktop image and
presented on the display
The contents of every
open window is stored in
video memory to facilitate
movement of windows.
Operating Systems
Wide range of systems - Example
There are 20 million cars on the road running QNX in various forms –
for their real-time engine monitoring to their built in entertainment
systems.
Cars use technologies including entertainment and real-time
monitoring, but are moving towards self-driving technology, parking
guidance and networked entertainment and information systems
All of this predicates a powerful OS
Key players are Microsoft (Windows Embedded Automotive), Google
(Android), Tizen [Samsung and Intel] (Linux), Audi (MMI)
See: http://www.forbes.com/sites/parmyolson/2013/01/03/among-thehot-trends-for-ces-2013-cars-that-run-on-android/
Operating Systems
Conclusion
 The “real-time OS” for “embedded systems” is an area of
much development at the moment
 Example: the old Sega Dreamcast games console ran
Windows CE OS (an early version of the MS Windows
Mobile OS)
 Smart cards, engine management systems, mobile
phones, Internet devices all run some kind of OS
 Wherever there is a CPU there is likely to be an OS of
some type