Operating Systems

1. Operating Systems 3.3.2

2. This presentation covers: • Different types of operating systems including: • Single-user • Multi-user • Multi-tasking • Interactive • Real-time • Batch processing • Distributed processing systems • The aim is to help you describe the features of each OS and understand their major characteristics.

3. Introduction • A lot of computer users understand that a computer needs an operating system (OS) ...but they don’t really understand WHY they are needed. • The OS is responsible for: • User interface • Memory management • CPU management • File management • Error detection • Utility software • Any installed applications, like the one you are using to view this presentation, will be calling upon the OS to access system resources. • Applications can’t control memory allocations, processing time etc...they need to ask the OS to do it for them.

4. Introduction • There are different types of operating systems out there too...each with a different role to play! • These include: • Single-user • Multi-user • Multi-tasking • Interactive • Real-time • Batch processing • Distributed processing systems

5. Introduction • Operating systems can be found in: • Digital watches • Calculators • Washing machines • Computer controlled microwave • Missile guidance systems • Mobile phones • Computer controlled burglar alarms • Some are generic, and some are purpose-built.

6. Single-user • Allows a single user to access any particular computer at any one time. • A few example single-user OS: • DOS • Windows • Linux • Don’t be confused with multiple accounts on a computer...for someone else to use their account you have to log off yours first! Sorry, but you’ll just have to wait until I am done! *grumble*

7. Multi-user • Allow lots of users to share data and resources at (apparently) the same time. • This is called a network. • A server controls how the computers run and communicate. • The server needs a Network Operating System (NOS).

8. Multi-user • A network allows multiple users to multi-task. • The set up usually consists of multiple single-user OS computers connected to a multi-user OS server. • UNIX is an example of OS that allows this to happen. • Dumb terminals are often used in businesses where data processing takes place.

9. Dumb Terminals (FYI stuff) • A computer that has: • Keyboard • Monitor • However, they lack the power and facilities of desktop computers as they do not have any independent data processing or storage capabilities.

10. Multi-tasking • Some operating systems allow you to open more than one application at a time. • e.g. You could be listening to music in iTunes whilst working on an essay in MS Word. • Many single-user operating systems allow users to run multiple applications. • Early operating systems, such as DOS, didn’t allow this to happen. • They were not complex enough. • Dos is a single-user single-task OS.

11. Interactive • Simply put... • This type of OS requires direct user interaction. Aw dude...you mean I actually HAVE to do something? Lame.

12. Real-time • Usually used in embedded application. • This means it is a system that runs inside another system for a specific task. • For example, most modern cars have ECU (Engine Control Units) built in. This control how the car performs under acceleration. These can be modified to change the behaviour of the car. • Cars also have other systems in place which monitor tyre pressures, grip, weather and light conditions...

13. A little bit of history! • Batch OS systems were used to process jobs one at a time. • People used to write programs on punch hole cards and feed them into a special card reader. • The OS would interpret these cards one at a time and select the correct compiler for them

14. Batch OS today! • The demand to process large quantities of data has never been greater. • More people use banks and have multiple accounts. • People used to keep their money under their mattress! • Good for single purpose jobs.

15. Distributed Processing • A brilliant example of this type of system can be found in Sony’s PlayStation 3. • The PS3 has a very powerful processor. • Scientists are making use of this power by asking people to accept a usage policy which turns their PS3 into a mini super computer. • They system performs calculations using the remaining processing power (which isn’t needed at the time). After the calculations have been completed the results are sent off to another computer. • The result of this distributed system is that months can be saved in processing data compared to using a single super computer to do it.

16. Distributed Processing • Some super computers have thousands of processors all working together...sharing the work load to produce very fast results from data inputs. • Compare this to the distributed system of the PS3 and you could probably see that if enough people allowed their PS3 system to be used results could be produced a lot faster than a super computer! • So far, scientists have been able to map out climate change in a matter of days rather than years and analyse complete DNA structures!

17. What to do now. • Write a definition for the following: • Single-user • Multi-user • Multi-tasking • Interactive • Real-time • Batch processing • Distributed processing systems • What is the difference between a single-user and multi-user OS? • How does a batch processing system differ from an interactive OS? • Describe the computer you have at home and the computer you use at school. For each, give a definition of it’s type. • TIP: How was DOS defined? Now I gotta do work?! Dude...you are so not as cool as I thought you were!