1. Computing system
Lesson Objective: Understand what is meant by a ‘computer system’
Learning Outcome: Define the key words and give a brief explanation for each.
Keywords: Input, output, storage, processing, DAC ADC, reliability, availability, MTBF, Hardware redundancy, RAID, disaster recovery.

2. What is a computer system?
A computer system is made up of hardware and software. Hardware is any physical component that makes up the computer. Software is any program that runs on the computer.

3. ??? A computer system ... Process Output Input e.g. Monitor, speakers
e.g. Keyboard, mouse
Storage
e.g. Hard drive, RAM

4. Which has a computer system?
Identify the input & output devices. What information is being processed?

5. Digital and Analogue (Real World)
Analogue data can be stored as writing, sound, …etc.
Digital data is stored as 0’s and 1’s
Digital information occurs in steps
Analogue information makes gradual changes

6. Digital and Analogue signals
Input
Output
Computer
Analogue Signals
DIGITAL ONLY!
Analogue Signals
Analogue
to Digital Converter
Digital to
Analogue Converter
No entry to Analogue

7. Reliability Many computer systems need a high degree of reliability.
For example:

8. Protecting against failures
Redundancy
Disaster recovery

9. Redundancy
Redundancy means having more than one device in case of breakdown.

10. Redundancy Example RAID storage

11. Disaster recovery
Some companies fully rely on computer systems (e.g. web commerce)
They have plans for what to do if major systems fail
Companies often have their own procedures or they employ other companies who can do it.

12. Example of disaster recovery: