System Software...
A software system is a system based on software forming part of a computer system (a combination of hardware and software). The term software system is often used as a synonym of computer program or software. The term software system is related to the application of systems theory approaches in software engineering context. This approach is often used to study large and complex software, because it focuses on the major components of software and their interactions. The term software system is also related to the field of software architecture.
Major categories of software systems include application software, programming software and system software, although the distinction can sometimes be difficult. Examples of software systems include computer reservations system, air traffic control software, military command and control systems, telecommunication networks, web browsers, content management systems, database management systems, expert systems, spreadsheets, theorem provers, window systems, word processors, etc. Software systems are an active area of research for groups interested in software engineering in particular and systems engineering in general.
A computer reservations system (CRS) is a computerized system used to store and retrieve information and conduct transactions related to air travel. Originally designed and operated by airlines, CRSes were later extended for the use of travel agents; major CRS operations that book and sell tickets for multiple airlines are known as global distribution systems (GDS). Airlines have divested most of their direct holdings to dedicated GDS companies, who make their systems accessible to consumers through Internet gateways. Modern GDSes typically allow users to book hotel rooms and rental cars as well as airline tickets.
Air traffic control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other support for pilots when able. In some countries, ATC may also play a security or defense role (as in the United States), or actually be run entirely by the military (as in Brazil). Air traffic control was first introduced at London's Croydon Airport in 1921. Archie League, who controlled aircraft using colored flags at what is today Lambert-St. Louis International Airport, is often considered the first air traffic controller.
Preventing collisions is referred to as separation, which is a term used to prevent aircraft from coming too close to each other by use of lateral, vertical and longitudinal separation minima; many aircraft now have collision avoidance systems installed to act as a backup to ATC observation and instructions. In addition to its primary function, the ATC can provide additional services such as providing information to pilots, weather and navigation information and NOTAMs (Notices to Airmen).
In many countries, ATC services are provided throughout the majority of airspace, and its services are available to all users (private, military, and commercial). When controllers are responsible for separating some or all aircraft, such airspace is called "controlled airspace" in contrast to "uncontrolled airspace" where aircraft may fly without the use of the air traffic control system. Depending on the type of flight and the class of airspace, ATC may issue instructions that pilots are required to follow, or merely flight information (in some countries known as advisories) to assist pilots operating in the airspace. In all cases, however, the pilot in command has final responsibility for the safety of the flight, and may deviate from ATC instructions in an emergency. To ensure communication, all pilots and all controllers everywhere are required to be able to speak and understand English. While they may use any compatible language, English must be used if requested. The native language for the region is normally used. FAA Control Tower Operators (CTO)/Air Traffic Controllers use FAA Order 7110.65S as the authority for all procedures regarding air traffic. For more information regarding Air Traffic Control rules and regulations, refer the Federal Aviation Administration's (FAA)
