1. Information Systems Design and Development Technical Implications (Software) Computing Science

2. Learning Outcomes By the end of this topic you will be able to: describe the functions of an operating system; understand the purpose of a software licence; explain the difference between proprietary and open source software; explain the difference between proprietary and open source software; explain what is meant by the term transferability; discuss current trends in the design of operating systems.

3. Functions of an operating system The main functions of an operating system are Interpreting user commands File management Memory management Input/output management Error reporting Resource allocation

4. Interpreting user commands User interface may be Command driven – require specific commands to be entered, normally by keyboard. Most suited to experienced users Menu driven – options available presented to user. May be text or graphical.

5. File management The part of the system that deals with managing backing storage devices When files saved it creates an entry giving details of location, file size, date saved etc. Organises files into hierarchical system with folders and sub-folders

6. Memory management The part of the system that controls where programs and data are placed in main memory Keeps track of available space and size and location of programs and data in main memory Allows multiple programs to be in main memory at the same time and prevents them from interfering with each other

7. Input/output management The part of the system that deals with communications between the processor and attached peripherals Handles the transfer of data between processor and peripherals Checks for readiness of peripherals Checks that data is transferred correctly

8. Error reporting The part of the system that displays error messages to the user

9. Resource allocation The part of the system that controls availabe resources for processes These resources will include available memory and processor time In systems with more than one process active it ensures that all processes get a share of available resources

10. Software licences A software licence is the permission to use a piece of software Using licenced software without a licence breaches the Copyright, Design and Patents Act The license will specify what you are allowed to do with the software. For example, can you install it on a single system, on several devices or on a site or a network

11. Software licences You normally have to agree to the conditions of the licence to be allowed to install software Not all software requires a licence. For example the Linux operating system is licence - free

12. Software licences Some software is available on a different basis Freeware – software available at no cost. Usually fully working programs with no time limitations Shareware – similar to freeware but will only work for a limited period before the user has to pay

13. Proprietary and Open Source Software Another way to classify software is Proprietary Open source

14. Proprietary software Proprietary or closed source software is software that is sold with conditions that prevent you from Sharing Copying Modifying The source code is not normally available to the user

15. Proprietary software Advantages Software is supported by software company More likely to be good quality Disadvantages Have to pay for it Can’t alter it Normally limiter to one operating system

16. Open source software Software that is made available with its source code Users can alter code Users can share code Code is often produced on a non-commercial basis by public bodies or groups of enthusiasts

17. Open source software Advantages Free to use, change and distribute Not dependent on single company for support. This makes updates and security fixes faster No need for anti-piracy measures like activation codes Disadvantages Less user friendly Far fewer applications run on open source operating systems

18. Software portability Software is portable if it can run on more than one operating system with little or no alteration. Portability is rare with commercial operating systems. Where the same software exists for different platforms, a different version will have to have been created. This is why, for example that there will be apps that are only available for iOS and not Android devices

19. Software Portability Java offers the ability to run sotware on different devices by using Java Virtual Machine software. Virtual machines are covered in more detail in the SDD unit Developments in web-based software have started to create true portable software

20. Current trends in Operating System development Developments driven by move to mobile devices Use of touch screens Cut down OS for mobile devices Cloud storage Wearable technology