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Design by contract (DbC), also known as contract programming, programming by contract and design-by-contract programming, is an approach for designing software. It prescribes that software designers should define formal , precise and verifiable interface specifications for software components , which extend the ordinary definition of abstract ...
In 1964 the GPO placed a contract for 10,000 units. [3] The Trimphone started life in 1964 as the Telephone No. 712, which was usually supplied as a 712L with an alphabetical as well as numerical dial. The Trimphone was the first in the GPO range to use a tone caller which warbled at around 2,350 Hz modulated by ringing current. The volume of ...
In the United States, a group purchasing organization (GPO) is an entity that is created to leverage the purchasing power of a group of businesses to obtain discounts from vendors based on the collective buying power of the GPO members. [1] Many GPOs are funded by administrative fees which are paid by the vendors that GPOs oversee.
The concept of Design by Contract, highly influential as a design and programming methodology concept and a language mechanism present in such languages as the Java Modeling Language, Spec#, the UML's Object Constraint Language and Microsoft's Code Contracts. The design of the Eiffel language, applicable to programming as well as design and ...
Command-query separation is particularly well suited to a design by contract (DbC) methodology, in which the design of a program is expressed as assertions embedded in the source code, describing the state of the program at certain critical times. In DbC, assertions are considered design annotations—not program logic—and as such, their ...
The GPO placed a contract in July 1950 for a chain of microwave links to feed BBC television from Manchester to the Kirk o' Shotts transmitting station. This was the first permanent GPO system to use the 4 GHz band. The chain was routed near the east coast in order to be close to Leeds, Newcastle and Edinburgh. The stations were at: [6]
Design by contract also includes notions of postcondition and class invariant. The precondition for any routine defines any constraints on object state which are necessary for successful execution. From the program developer's viewpoint, this constitutes the routine caller's portion of the contract.
The General Post Office (GPO) [1] was the state postal system and telecommunications carrier of the United Kingdom until 1969. [2] Established in England in the 17th century, the GPO was a state monopoly covering the dispatch of items from a specific sender to a specific receiver (which was to be of great importance when new forms of communication were invented); it was overseen by a ...