1. Operating Systems
p.describe the characteristics of knowledge-based systems;
q.describe the purpose of operating systems;
r.describe the characteristics of different types of operating systems and their uses: batch, real-time, single-user, multi-user, multi-tasking and distributed systems;
s.describe a range of applications requiring batch processing, and applications in which a rapid response is required;

2. Applications Software
Operating system
An Operating System (OS) is a piece of software that manages the computer's hardware and provides common services (memory allocation etc) to applications software and Users.
Common Operating Systems include Microsoft Windows, Linux, Mac OS X.
User
Applications Software
Operating System
Hardware

3. Types of OS
There are many different types of operating system each with very different capabilities.
Some of the different types:
Single user, single process
Multi-programming
Multi-user
Batch
Real time
6. Knowledge based

4. Single User - Single Process
The operating system supervises the loading and running of one program at a time as well as the input and output of data from peripheral devices.
Used in simple manufacturing environments.

5. Multi-programming\ Multi-tasking
Multi Programming is defined as the apparent simultaneous execution of two or more programs.
A Multi-programming operating system enables two or more programs to be held in memory at the same time. Each program is given a small amount of processor time before moving to the next program.
This system makes efficient use of valuable processor time because when one program is held up waiting input\output the processor can be allocated to another program.
It is the job of the operating system to maximise throughput while ensuring all jobs are completed in a reasonable time.

6. Multi - user
A multi user operating system is defined as one that allows two or more users to communicate with the computer at any one time.
Each user has their own monitor, keyboard etc but connects to the same computer.
The processor gives a small amount of time to each user before moving on, as long as there aren't too many users each user has the impression only they are using the system.

7. Batch
In Batch operating systems a job runs from beginning to end without intervention from the user.
The running of Batch jobs is controlled by a program written in a JCL which specifies things like job priority, print lines, execution time required etc.
Multi-programming systems were first developed so many Batch jobs could be run simultaneously.

8. Real time systems
Real-time systems are used when data input must be processed immediately.
Some times a delay of a few seconds is acceptable (ie booking your flight) sometimes it’s not (when the pilot wants to land).

9. Knowledge based systems
Knowledge based systems (expert systems) attempt to replicate human knowledge on a specific area. They are able to store information and help users solve a problem.
The main features of an expert system are:
1.Limited a specific area of expertise.
2. Rule based.
3. Delivers advice.
Knowledge based systems consist of:
A knowledge base of facts
An interface
3. A way of using or manipulating the facts they have stored