Algorithms and Flowcharts : Introduction

An algorithm is a description of how to carry out a process. An algorithm lists the steps that must be followed to complete the process. Algorithms can be described using a language such as English. Here is an algorithm which describes how to make a telephone call :

1. Lift telephone handset.
2. If there is no dialling tone then go to 10.
3. Dial number.
4. If number is engaged or unavailable then go to 10.
5. If correct person answers telephone then go to 8.
6. Ask to speak to correct person.
7. If correct person not available go to 9.
8. Hold conversation.
9. Say goodbye.
10. Replace handset.

Descriptions like this are often ambiguous and open to misunderstanding. Therefore various formal methods of describing algorithms have been developed. The simplest methods are the flowchart and the system flowchart.

GCSE ICT Companion 04 - (C) P Meakin 2004