This document discusses operating systems and software development. It defines the main functions of an operating system as memory management, user interface, multi-tasking, peripheral management, and security. It also describes different types of software development including custom written, off-the-shelf, open source, and proprietary software. The document provides examples of benefits and limitations of each approach.

1. Software
GCSE Computing Theory

2. Get your brains logged on!
Which is the odd one out?

3. Get your brains logged on!
Which is the odd one out?

4. By the end of this lesson:
• All of you be able to explain the main functions
of an operating system.
• Most of you will be able to describe the purpose
and use of common utility programs for security
and maintenance.
• A few of you will explore the differences between
custom written, off the shelf, open source and
proprietary software.

5. Main functions of an OS
• Think MUMPS!
• Memory management
• User interface
• Multi-tasking
• Peripheral management
• Security

6. Memory Management
• The OS manages the transfer of data
between the CPU, RAM and main storage
(e.g. hard drive)

7. User interface
• The OS provides the user with a way of
controlling the functions of the computer
without resorting to machine code.
• It can be:
Graphical (GUI – Graphic User Text-based [no mouse] (CLI –
Interface), e.g. Windows Command Line Interface), e.g. MS-DOS

8. Multi-tasking
Word processor
Virus scanner
Operating
System
Email (OS)
Web browser CPU

9. Peripheral Management
Operating
System (OS)

10. Security
• The OS provides security features to
restrict access to the system or particular
files.

11. Your Task:
• Write down the answer to the following
question (you can use the notes to help):
• Describe the main functions of an
Operating System.

12. Utility Programs
• Utility software is system software
designed to help analyze, configure,
optimize or maintain a computer.
• A single piece of utility software is usually
called a utility or tool.
Card sort: Match the utility tool to its description.
Group the utilities into security and maintenance.
Source: Wikipedia.org

13. Software Development
• For main routes to software development:
–Custom written / bespoke
–Off-the-shelf
–Open source
–Proprietary

14. Custom written / bespoke
• Developed specifically for a particular
organisation
Benefits Limitations
Custom-made to meet Very expensive to
the exact purpose produce and need
technical expertise to
develop.

15. Off-the-shelf
• Developed by a software company to be
sold to the general public, e.g. MS Office.
Benefits Limitations
Cheaper than Inflexible – software
developing it yourself might not do
and tech support everything you want
available. May not it do.
have skills in
organisation to
develop yourself.

16. Open source
• Written by general public for everyone else
to use. Source code provided so software
can be tweaked.
Benefits Limitations
Allows anyone to As source code can
use/adapt the be viewed, could
software to meet their provide opportunity
needs. Collaborative for people to “take
approach to advantage” and
development. compromise security.

17. Proprietary
• Written by developer and allowed to be used by
others but with certain restrictions, e.g. can’t
adapt software. Source code is hidden.
Benefits Limitations
Can allow for different Source code cannot
versions of same be looked at so may
software, e.g. contain spyware or
educational version other malicious
with limited features hidden within
functionality. the software.

18. Test your knowledge
• Karen wants to use handheld computers
to take customers’ orders in her
restaurant. She is thinking of using custom
written software.
a) State what is meant by custom written
software.
b) State two reasons why Karen may decide to
use custom written software.

19. Test your knowledge
a) Software created especially for a user/the
restaurant
b) Two from:
– Appropriate software may not exist
– Existing software may not do exactly what
restaurant wants
– Existing software may not be compatible with
restaurant’s hardware
– Existing software may contain additional
features (more complex and expensive)