Large-scale system

Definition
Large-scale systems are

"IT systems that contain many (thousands, millions, billions, or trillions or more) interacting hardware and software components. They tend to be heterogeneous &mdash; in that they are composed of many different types of components &mdash; and highly complex because the interactions among the components are numerous, varied, and complicated. They also tend to span multiple organizations (or elements of organizations) and have changing configurations."