244Chapter8 • Cross-Platform and Embedded Systems Development
many modern operating systems are also being used in embedded systems these days. Embed-
ded Linux products are becoming more and more popular.
Since embedded systems are used for special purpose tasks, there is usually no need to add
new applications to the system once it is built. Therefore programs and operating systems are
usually loaded only once into read-only memory. The read-only memory is available in many
forms these days and includes some type of ROM, flash chips and flash cards. In case an
upgrade is required, a new ROM chip replaces the old one.
If you look at your surroundings, you will find tiny computers everywhere. They are
present even in places where you rarely notice them. Some of the most common embedded sys-
tems used in everyday life are:
•Refrigerators
•Microwave ovens
•TV, VCR, DVD players
•Cameras
•Cars (Antilock brakes, engine control, sun roof, climate control, automatic
transmission and so on)
•Personal digital assistants
•Printers
Complicated and more sophisticated embedded systems include routers and switches
where high performance CPUs are used.
8.2.1Embedded Systems and Moving Parts
Most of the embedded systems are supposed to be used for a long period of time and with-
out any maintenance. This is the very nature of embedded systems applications, to manufacture
a system and then leave it to run independently for its intended life. For this reason, most
embedded systems usually don’t have moving components because any moving or mechanical
part experiences wear and tear and needs replacement periodically. Typical examples of moving
components include fans, disk drives and so on. Fans are used for cooling in power supplies and
CPU heat sinks in desktop computers. Disk drives (both floppy and hard disk drives) are used as
a storage medium for operating systems, applications and data.
In embedded systems, ROM is used for storage of operating system and application data
to eliminate the need for disk drives. These days, flash cards are also common and you can
update a system just by replacing the flash memory card. In embedded systems you have to use
special types of power supplies that don’t need any fan for cooling. Many different types of
power supplies are available on the market that don’t heat up when used continuously for long
periods of time.