Classes of computers

These traditional minicomputers in the last few decades of the 20th century, found in small to medium-sized businesses, laboratories and embedded in (for example) hospital CAT scanners, often would be rack-mounted and connect to one or more terminals or tape/card readers, like mainframes and unlike most personal computers, but require less space and electrical power than a typical mainframe.

A supercomputer is focused on performing tasks involving intense numerical calculations such as weather forecasting, fluid dynamics, nuclear simulations, theoretical astrophysics, and complex scientific computations.

In terms of computational capability, memory size and speed, I/O technology, and topological issues such as bandwidth and latency, supercomputers are the most powerful, are very expensive, and not cost-effective just to perform batch or transaction processing.

A server is expected to be reliable (e.g. error-correction of RAM; redundant cooling; self-monitoring, RAID), fit for running for several years, and giving useful diagnosis in case of an error.

A server may run several virtual machines (VMs) for different activities, supplying the same environment to each VM as if it ran on dedicated hardware.

This technology approach needs special hardware support to be useful and was first the domain of mainframes and other large computers.

Nowadays, most personal computers are equipped for this task, but for long-term operation or critical systems, specialized server hardware may be needed.

Information appliances are computers specially designed to perform a specific "user-friendly" function—such as editing text, playing music, photography, videography etc.

Embedded computers generally execute a program that is stored in non-volatile memory and is only intended to operate a specific machine or device.

Embedded computers are typically required to operate continuously without being reset or rebooted, and once employed in their task the software usually cannot be modified.

This user often may use all hardware resources, has complete access to any part of the computer and has rights to install/remove software.

Some computers in a business setting are for one user but are also served by staff with protocols to ensure proper maintenance.