Operating systems can be grouped according to functionality: operating systems for supercomputing, render farms, mainframes, servers, workstations, desktops, handheld devices, real time systems, or embedded systems.
* Supercomputing is primarily scientific computing, usually modelling real systems in nature. Render farms are collections of computers that work together to render animations and special effects. Work that previously required supercomputers can be done with the equivalent of a render farm.
* Mainframes used to be the primary form of computer. Mainframes are large centralized computers. At one time they provided the bulk of business computing through time sharing. Mainframes and mainframe replacements (powerful computers or clusters of computers) are still useful for some large scale tasks, such as centralized billing systems, inventory systems, database operations, etc. When mainframes were in widespread use, there was also a class of computers known as minicomputers which were smaller, less expensive versions of mainframes for businesses that couldn’t afford true mainframes.
* Servers are computers or groups of computers used for internet serving, intranet serving, print serving, file serving, and/or application serving. Servers are also sometimes used as mainframe replacements.
* Desktop operating systems are used for personal computers.
* Workstations are more powerful versions of personal computers. Often only one person uses a particular workstation (like desktops) and workstations often run a more powerful version of a desktop operating system, but workstations run on more powerful hardware and often have software associated with larger computer systems.
* Handheld operating systems are much smaller and less capable than desktop operating systems, so that they can fit into the limited memory of handheld devices.
* Real time operating systems (RTOS) are specifically designed to respond to events that happen in real time. This can include computer systems that run factory floors, computer systems for emergency room or intensive care unit equipment (or even the entire ICU), computer systems for air traffic control, or embedded systems. RTOSs are grouped according to the response time that is acceptable (seconds, milliseconds, microseconds) and according to whether or not they involve systems where failure can result in loss of life.
* Embedded systems are combinations of processors and special software that are inside of another device, such as the electronic ignition system on cars.