Finally, mobile computer systems are likely to be aware of, or embedded into their physical surroundings. Often this is because they are embedded in an application specific device, for example in a mobile phone or car. In these situations the computer system is mobile by virtue of being part of a larger mobile artefact. This context can and
does affect the application interface, for example, the telephone directory within a mobile phone can be very
different from one in an independent PDA. Another example is a car radio (now often computer controlled) which
has different design considerations to a static radio including the need to automatically retune as the car travels
between local radio areas and transmitter zones. Because the computer systems are embedded into application
specific devices they may also be aware of their environmental context, for example, the speed of the car. Some of
this sensory information may be used simply to deliver information directly to the user, but others may be used to
modify interface behaviour. For example, in a tourist guide, increasing text size in poor lighting conditions or, in a
car system, limiting unimportant feedback during periods of rapid manoeuvring