High Quality Content by WIKIPEDIA articles! Ultra-large-scale system (ULSS) is a term used in fields including Computer Science, Software Engineering and Systems Engineering to refer to software intensive systems with unprecedented amounts of hardware, lines of source code, numbers of users, and volumes of data. The scale of these systems gives rise to many problems: they will be developed and used by many stakeholders across multiple organizations, often with conflicting purposes and needs; they will be constructed from heterogeneous parts with complex dependencies and emergent properties; they will be continuously evolving; and software, hardware and human failures will be the norm, not the exception. The term `ultra-large-scale system` was introduced by Northrop and others to describe challenges facing the United States Department of Defense. The term has subsequently been used to discuss challenges in many areas, including the computerization of financial markets. The term `ultra-large-scale system` (ULSS) is sometimes used interchangeably with the term `large-scale complex IT system` (LSCITS). These two terms were introduced at similar times to describe similar problems, the former being coined in the USA and the latter in the UK.