Computer are used to control the operation of many and everyday objects. The instructions contained in the computer program send signals out to computer to devices like switches and motors which make the machine operate in correct way.

One programming language used to control the movement of simple objects is Logo. This language was designed for pupils in juniors schools and can make mechanical ‘turtle’ move around the floor on a sheet of paper (or an image onscreen). The turtle has a pen which can lowered on to the paper so that a trail is left as the turtle moves across the paper. Some of the instructions From Logo are shown below:

FORWARD n Move ‘n’ steps forwardBACKWARD n Move ‘n’ steps backwardRIGHT d Turn ‘d’ degrees to the rightLEFT d Turn ‘d’ degrees to the leftPENUP Lift the pen off the paperPENDOWN Lower the pen down onto the paper

Feedback is the term used in computer control when data input from a sensor causes the control program to make changes by sending signals to output devices. These changes are then recorded by the input sensor and data signal sent back to the computer.

For example to place boxes in position using an automated system:

do until box in positionmove box forwardcheck position

loop

When a computer is used to control a machine, the computer circuit board is installed inside the machine. The input sensors and output control decides are then connect to these circuits. This is an embedded computer. The input/output devices that we are most familiar with – the keyboard, mouse, monitor and disk drive – are not required.

The computer control program is written using a ‘normal’ computer and ‘downloaded’ into the embedded computer. The software pogrom is stored in a ROM (read only memory) chop and activated when the machine is switched on.

Advantages of using computers for control:

•Cheaper to run computerised machines than to employ people

•Computers don’t need break or sleep

•Quality of work produced from the machine is consistent

•Machines can cope with very heavy work and precise work

•Uncomfortable and hostile places for people, can have machines working in them

•Machines can work faster due to computers processing data very quickly

•Computers can operate machines with data from a range of sources

Disadvantages of using computers for control:

•Expensive to run