What is an embedded system?

An embedded system is a special-purpose computer system which resides inside the device or equipment it manages or controls. An embedded system has certain pre-defined tasks and specific constrains, thus differing from the general purpose PC computer.

Examples of Embedded Systems

In-vehicle computers
Portable measurement equipment
Panel computers
Printers
Network equipment
PDA, cellular phones

Characteristics

Special microprocessors are used in embedded systems to reduce cost for mass production. These microprocessors have simplified architecture, low performance and low cost comparing to general-purpose processors such as the Intel Pentium. For example, a standard 10MHz microprocessor used in embedded systems may cost around $1. Besides, an embedded system incorporates only the minimal amount of memory (RAM and ROM). While a desktop PC may have hundreds of megabytes of RAM and gigabytes of ROM (hard drive or DVD), a low-cost embedded system usually has just a few kilobytes of memory. Embedded systems are designed to operate for years without crashes, data loss and user intervention. Moving mechanical parts such as a CD drive or a hard drive are replaced with solid-state parts such as flash memory.

Processor Architectures

There are different kinds of processors used in embedded systems: digital signal processors (DSPs), microprocessors, microcontrollers. Unlike desktop PC market with dominating Intel/AMD x86 architecture, the ARM, XScale, PowerPC, MIPS, x86, PIC, AVR, Coldfire/68k, 8051 architectures are widely used on the embedded market.

Operating Systems

Complex systems with rich functionality employ special operating systems that take into account major characteristics of embedded systems. Embedded operating systems have minimized footprint and may follow real-time operating system specifics.

General purpose operating systems such as Linux or Windows, adapted to embedded systems, became increasingly popular. VxWorks and QNX are the examples of commercial real-time operating systems. Embedded Linux, Windows CE, Windows XP Embedded and NetBSD are the examples of adapted general purpose systems.