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What is an...

• Embedded system?
• Real-Time system?
• What is a Safety-Critical system?
• What Standards are used in Safety-Critical Systems ?
• What is a Client-Server system?
• What is Offshoring?

What is an Embedded system?

An embedded system is a component made of some electronics and software that is installed into a piece of equipment to make it provide certain functionality. These components are often required to have a high reliability sometimes being required to operate for years at a time without any human intervention. In the modern world such items are found around us everywhere but often remain unnoticed until they go wrong.

Examples of embedded systems range from the control of simple consumer products such as a microwave oven, washing machines or digital TV's, to more challenging systems such as those helping control car engines and anti-lock brakes, aircraft systems such as landing gear controls and navigation systems.

What is a Real-Time system?

A real-time system is one where a combined software and hardware component must provide its functionality within a defined time-frame, consistently, and irrespective of any other activities taking place. For example, the anti-lock brake system on a car must always respond within say 20milliseconds of the driver pressing the brake pedal. It cannot be 75 milliseconds then perhaps 100millisends of pressing the pedal; it must always be 20milliseconds.

What is a Safety-Critical system?

This is where a failure of the system can lead to the loss of human life.

Such systems have to be carefully analysed and designed to minimise the probability of such a failure occurring and to mitigate the risk.

Depending on the reliability requirements such systems can be designed to address the perceived hazard in different ways. For example the software and hardware are often designed so that it requires a combined failure of both the hardware and software before a hazardous event occurs.

Some systems can fail to a 'safe' state such as a pneumatic rail braking system where the brakes are held off by a vacuum. If there is a leak in the pipes so the vacuum cannot be maintained the air coming into the pipes causes the brakes to be applied automatically with no intervention from the driver, and the train to come to a safe stop.

Some safety-critical systems have to keep operational even when a failure has occurred. Some systems degrade to a get-you-home mode. Other systems might have to keep fully operational, in which case there may be several copies of the same components each cross-checking the behaviour of the others. If one copy behaves differently to the others then it is ignored and the system keeps operational.

What Standards are used in Safety-Critical Systems?

Due to the potentially serious consequences involved the development of safety-critical systems is very carefully regulated in all the sectors where it applies. The safety-critical development standards appropriate to different market sectors describe the characteristics required of the development process and the checks that must be made to ensure that the process has been followed.

Example standards:

What is a Client-Server System?

This is an IT system where there are three distinct components:

What is Offshoring?

There are several interpretations but in general it refers to the cross-border provision of services.

Offshore activities can be performed within an organisation through an in-house subsidiary, or externally through third party suppliers.

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© 2011 Project Realization Ltd
Acknowledgements to A Viklund and L Cvrk