W A L T - What is a system flowchart?  System flowcharts are a way of displaying how data flows in a system and how decisions are made to control events.data  To illustrate this, symbols are used. They are connected together to show what happens to data and where it goes.  Robots – how are they controlled?

The basic shapes include:

Using correct symbols: Start and Stop Decision Input and Output Process

This system flowchart is a diagram for a 'cruise control' for a car. The cruise control keeps the car at a steady speed that has been set by the driver system flowchart The flowchart shows what the outcome is if the car is going too fast or too slow. The system is designed to add fuel, or take it away and so keep the car's speed constant. The output (the car's new speed) is then fed back into the system via the speed sensor. output sensor

Other examples of uses for system diagrams include:  aircraft control  central heating  automatic washing machines  booking systems for airlines

John gets up

Microwave breakfast

He jumps in his car – he has a satellite navigation system. It tells him to avoid Main South Road as there is a traffic jam

Gets to work and pulls up at the car park barrier.

Control system for a car park barrier: Steps might be:  Start (don’t forget yes or no)  The driver presses the button on the machine OR the driver puts a card into the machine (input).  A ticket comes out of the slot on the machine (output)  The barrier opens (output)  The barrier stays open for 30 seconds (process) What happens if it is wrong??

On his way home he goes to the Supermarket (Pak’nSave at Hornby) the doors open automatically at the Mall. He grabs food out of the freezer – the freezers are kept at a constant temperature all day and all night. He goes to pay – puts his food on a conveyer belt and it moves up to the cashier and stops. He pays using his EFTPOS card and sets off home

How many control systems were there? Did you notice they all needed some way of being switched on and told what to do. Quite a lot of the devices used buttons or keypads of some sort.

Inputting instructions  His microwave worked out when 2 minutes have passed  His cellphone alarm worked out it is 6 am.  How did the car park barrier know when to open?  How did the supermarket doors know when to open?  NEXT STEP - we are going to use Flowol 4 to make our own flowcharts. First up

The instructions for a lift: The instructions that the computer follows could just be written in a list like this: 1. If someone presses the “Open” button then the doors should open. 2. The doors should stay open for a few seconds and then close again. 3. If no-one presses any buttons, then the doors should stay closed.