Special Purpose Computer Systems

There are various classes of computer systems based upon their computational speed, usage and hardware. The following are some special purpose systems according to specific applications. They use:

1. Real-time embedded systems Multimedia systems
2. Multimedia systems
3. Hand held and portable systems

These are explained as following below.

1. Real-time embedded systems Multimedia systems:
   Embedded systems are small computers having a limited set of hardware like a small processor capable of processing a limited set of instructions (often called as an Application Specific Integrated Circuit (ASIC) a small memory (RAM or EPROM) and I/O devices. These systems usually do specific tasks.

   Examples are microwave ovens, robots in a manufacturing unit, latest automotive engines, etc.

   A variety of embedded systems exists of which some are computers with standard operating systems, some have dedicated programs embedded in their limited memories and often some don’t even have any software, hardware (ASIC) to do processing. Nearly all embedded systems use real-time operating system because they are used as control devices and have rigid time requirements. Sensors are used to input data such as temperature, air pressure, etc, from the environment to embedded system where that data is analyzed and several other controls are adjusted by embedded system itself to control the situation of system.

   Few examples are home appliance controllers, weapon controllers, boiler temperature controllers, fuel injection system in automobile engines, etc. A real-time system needs that processing to be done in fixed time constraints.

2. Multimedia systems:
   Multimedia refers to data of multiple types that includes audio and video including conventional data like text-files, word-processing documents, spreadsheets, etc. It requires that audio and video data must be processed based upon certain time restrictions. This is called as streaming. It is usually 30 frames per second for a video file.

   Applications such as video conferencing, movies and clips downloaded over internet, mp3, DVD, VCD playing and recording are examples of various multimedia applications. A multimedia application is usually a combination of both audio and video. The multimedia is not limited to desktop operating system or computers but it is also becoming popular in handheld.

3. Hand held and portable systems:
   Hand-held systems refers to small portable devices that can be carried along and are capable of performing normal op erations. They are usually battery powered. Examples include Personal Digital Assistants (PDAs), mobile phones, palm-top computers, pocket-PCs etc. As they are handheld devices, their weights and sizes have certain limitations as a result they are equipped with small memories, slow processors and small display screens, etc.

   The physical memory capacity is very less (512 KB to 128 MB) hence the operating systems of these devices must manage the memory efficiently. As the processors are slower due to battery problem, the operating system should not burden.