Software systems

A software system is a system whose elements are chiefly software, built and operated to serve some purpose for its users and stakeholders. It’s the broad umbrella under which most of software engineering’s concerns — design, architecture, testing, deployment — apply. A single running application, a distributed platform of many services, and an embedded controller are all software systems, differing mainly in shape and constraints rather than in kind.

Software systems are commonly grouped into a few typical categories, distinguished by how and when they process work.

• Batch systems process accumulated input in scheduled runs rather than immediately — see batch processing.
• Interactive online systems respond to individual requests as they arrive, typically from a human user or another system, within a short and often bounded time.
• Embedded real-time systems run as part of a larger piece of hardware, on an embedded system, and must react to events within strict timing deadlines, where a late response is treated as a failure of the system.

These categories are not mutually exclusive labels for whole systems so much as different processing modes a system can combine. A platform might serve interactive requests in real time while also running nightly batch jobs. But naming them helps set expectations early about a system’s non-functional requirements, particularly around latency, throughput, and failure tolerance.