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Terminology

These routines use the terminology ``item'' to refer to either a structured noticeboard object (ie, one with no values but possibly having lower-level objects) or to a primitive noticeboard object (ie, one with a shape and with values). The terms ``item identifier'', ``identifier'' or ``ID'' refer to ``handles'' (cf HDS locators) which allow access to all information pertaining to an item. As far as callers are concerned these are just integers. As far as the noticeboard system is concerned they are pointers to data structures called ``item_descriptor''s. In the routine specifications they are regarded as integers. A zero ID is always an invalid ID and all routines will detect an attempt to use a zero ID. Similarly all routines that return ID's will return zero ID's on failure. Note that there is a danger of an access violation if true garbage ID's are passed. This is unlikely to happen, because of the use of the modified status convention.



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Next: Examples of Using the NBS Routines
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NBS The Noticeboard System
Starlink User Note 77
D.J. Allan
11 September 1995
E-mail:ussc@star.rl.ac.uk