16th lecture: 9/9/09

Lecture today still is telecommunication, but Miss Noorazura is teaching Facsimile System and Paging System.
Facsimile System is a copy or reproduction of an old book, manuscript, map, art print or other item of historical value that is as true to the original source as possible using, normally, some form of photographic technique. It differs from other forms of reproduction by attempting to replicate the source as accurately as possible in terms of scale, color, condition, and other material qualities. For books and manuscripts, this also entails a complete copy of all pages; hence an incomplete copy is a "partial facsimile". Facsimiles are used, for example, by scholars to research a source that they do not have access to otherwise and by museums and archives for museum and media preservation. Many are sold commercially, often accompanied by a volume of commentary. They may be produced in limited editions, typically of 500–2,000 copies, and cost the equivalent of a few thousand United States dollars.
Paging System is an important part of virtual memory implementation in most contemporary general-purpose operating systems, allowing them to use disk storage for data that does not fit into physical RAM. Paging is usually implemented as architecture-specific code built into the kernel of the operating system. In computer operating systems there are various ways in which the operating system can store and retrieve data from secondary storage for use in main memory. One such memory management scheme is referred to as paging. In the paging memory-management scheme, the operating system retrieves data from secondary storage in same-size blocks called pages. The main advantage of paging is that it allows the physical address space of a process to be noncontiguous. Prior to paging, systems had to fit whole programs into storage contiguously which caused various storage and fragmentation problems.