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Multics

Multics is an influential early time-sharing operating system, based on the concept of a single-level memory. All modern operating systems were influenced by Multics – through Unix, created by some of the people who had worked on Multics – either directly or indirectly. Initial planning and development for Multics started in Cambridge, Massachusetts, it was a cooperative project led by MIT along with General Electric and Bell Labs. It was developed on the GE 645 computer, specially designed for it. Multics was conceived as a commercial product for General Electric, became one for Honeywell, albeit not successfully. Due to its many novel and valuable ideas, Multics had a significant impact on computer science despite its faults. Multics had numerous features intended to ensure high availability so that it would support a computing utility similar to the telephone and electricity utilities. Modular hardware structure and software architecture were used to achieve this; the system could grow in size by adding more of the appropriate resource, be it computing power, main memory, or disk storage.

Separate access control lists on every file provided flexible information sharing, but complete privacy when needed. Multics had a number of standard mechanisms to allow engineers to analyze the performance of the system, as well as a number of adaptive performance optimization mechanisms. Multics implemented a single-level store for data access, discarding the clear distinction between files and process memory; the memory of a process consisted of segments that were mapped into its address space. To read or write to them, the process used normal central processing unit instructions, the operating system took care of making sure that all the modifications were saved to disk. In POSIX terminology, it was. All memory in the system was part of some segment. One disadvantage of this was that the size of segments was limited to 256 kilowords, just over 1 MiB; this was due to the particular hardware architecture of the machines on which Multics ran, having a 36-bit word size and index registers of half that size.

Extra code had to be used to work on files larger than this, called multisegment files. In the days when one megabyte of memory was prohibitively expensive, before large databases and huge bitmap graphics, this limit was encountered. Another major new idea of Multics was dynamic linking, in which a running process could request that other segments be added to its address space, segments which could contain code that it could execute; this allowed applications to automatically use the latest version of any external routine they called, since those routines were kept in other segments, which were dynamically linked only when a process first tried to begin execution in them. Since different processes could use different search rules, different users could end up using different versions of external routines automatically. With the appropriate settings on the Multics security facilities, the code in the other segment could gain access to data structures maintained in a different process. Thus, to interact with an application running in part as a daemon, a user's process performed a normal procedure-call instruction to a code segment to which it had dynamically linked.

The code in that segment could modify data maintained and used in the daemon. When the action necessary to commence the request was completed, a simple procedure return instruction returned control of the user's process to the user's code. Multics supported aggressive on-line reconfiguration: central processing units, memory banks, disk drives, etc. could be added and removed while the system continued operating. At the MIT system, where most early software development was done, it was common practice to split the multiprocessor system into two separate systems during off-hours by incrementally removing enough components to form a second working system, leaving the rest still running the original logged-in users. System software development testing could be done on the second system the components of the second system were added back to the main user system, without having shut it down. Multics supported multiple CPUs. Multics was the first major operating system. Despite this, early versions of Multics were broken into repeatedly.

This led to further work that made the system much more secure and prefigured modern security engineering techniques. Break-ins became rare once the second-generation hardware base was adopted. Multics was the first operating system to provide a hierarchical file system, file names could be of arbitrary length and syntax. A given file or directory could have multiple names, symbolic links between directories were supported. Multics was the first to use the now-standard concept of per-process stacks in the kernel, with a separate stack for each secur

St Paul's Catholic College (Burgess Hill)

St Paul's Catholic College is a comprehensive Catholic secondary, sixth form college in the town of Burgess Hill in West Sussex, England. The college first opened on 9 September 1963 as a modern secondary school serving the Mid-Sussex area, it was situated in the nearby town of Haywards Heath, but relocated to its current site at the northwestern edge of Burgess Hill in September 2004. Took place in 2013-2014 to mark 50 years since the school opened. In April 2013 the College was appointed as a National Teaching School and National Support School by the Department for Education. 350 schools nationally have taken on this leadership role. This is a responsibility to lead teacher training, professional development and development, raising achievement and school to school support. There is a clear commitment to support schools in requiring improvement; this is led through the Inspire Teaching School Alliance. St. Paul's is a Sports College and has Leading Edge status as a high performing secondary school.

The college accepts children from the age of eleven through to eighteen, accommodates 1000 students. There were five houses: Corinth, Damascus and Rome, as the school expands student numbers to 1,050 students by 2014; each form is a place significant to St. Paul's life; the school has played a role in advancing the role of e-learning in the classroom, as well as being a fair-trade school, encouraging student support for good causes, both locally and worldwide. Results have been strong at GCSE and A-level and the College has been named within the highest performing secondary schools nationally. There is a strong belief that education should be about developing the "whole person" by looking to develop student confidence, happiness and academic success. St Paul's was first graded as'outstanding' by Ofsted in 2007. Subsequently further reports in 2008 and 2011 confirm that St Paul's remains an'outstanding school', it was graded as'outstanding' in the Section 48 inspection by the diocese which evaluates the quality of Catholic education and the spiritual life of the school most in 2014.

St Paul's Catholic College Website St Paul's Catholic College Sixth Form Website St Paul's Professional Centre St Paul's VLE Inspire Teaching School Alliance

21 cm K 12 (E)

The 21 cm Kanone 12 in Eisenbahnlafette was a large German railroad gun used in the Second World War and deployed on the English Channel coast in occupied France. Krupp continued theoretical research on a replacement for the Paris Gun during the Weimar Republic-era, but it was the Nazi government that authorized funding for experiments to solve some of its worst problems; the high velocities used by the Paris Gun to attain the stratospheric heights necessary for extreme range caused enormous wear of the barrel, so much so that the shells had to be made in increasing diameter to suit the rate of wear. Barrel life was 65 rounds, it is believed that the one Paris Gun destroyed by a premature detonation in the bore was caused by loading one of the serially-numbered shells out of order. Thus Krupp decided to use only eight grooves in the barrel and to machine matching ribs or splines on the shells to eliminate the need for a massive copper driving band to start the shell spinning without shearing off, one of the prime causes of the excessive barrel wear in the earlier weapon.

Gas sealing would be handled by a copper band, mounted in the place occupied by the driving band, with an asbestos and graphite packing to form the initial seal. Several test barrels, known as the 10.5 cm K 12 M, shells were made in 1935 and were compared to a conventionally rifled barrel. The tests proved; the K 12 was mounted on a simple box-girder carriage, carried on two subframes which were in turn mounted on double bogies. The barrel was mounted in a ring cradle with a hydropneumatic recoil system. Two more hydropneumatic systems were connected to the subframes, which allowed the entire carriage to recoil some 98 centimetres. For transport the gun itself was disconnected from its recoil system and drawn back some 1.5 metres to reduce the mounting's overall length and allow it to fit in the normal railroad loading gauge. The barrel's extreme length required external bracing to prevent it from bending under its own weight, its trunnions were placed as far forward as possible to balance the barrel and minimize the force necessary to elevate it.

This placed the breech perilously close to the ground and a hydraulic jacking system was built in each subframe to elevate the mount 1 metre. However it was impossible to load the weapon in this position and it had to be lowered between every shot; the K 12 could be fired from any curved section of track, a Vögele turntable, or from its special firing track. This prefabricated T-shaped track was carried on the gun train and deployed by a special crane wagon. Once the front bogies were at the crossover at the top of the T they were jacked up and turned with the subframe 90° and lowered onto the crosstroke of the T; the gun was traversed by an electric motor to the bogies and it was clamped to the track once laid onto the target. It fired HE shells weighing 107.5 kilograms. The first weapon was completed in 1938 and delivered to the Army in March 1939, it was successful, although the necessity to jack it up and down between shots was not well received by the Heer. Krupp discovered, on trying to rectify this problem, that hydro-pneumatic balancing-presses could work at much greater weights and pressures than believed.

They redesigned the mounting with the trunnions as far forward as possible and increased the recoil stroke to 150 centimetres. The new design was delivered in mid-1940 and called the K 12 N; the first gun was retrospectively called the K 12 V. They spent the war assigned to Artillerie-Batterie 701 along the Channel coast; the British recovered shell fragments near Rainham, Kent, 88 kilometres from the nearest point on the French coast. Engelmann, Joachim. German Railroad Guns in Action. Carrollton, Texas: Squadron/Signal, 1976 ISBN 0-89747-048-6 Engelmann and Scheibert, Horst. Deutsche Artillerie 1934–1945: Eine Dokumentation in Text, Skizzen und Bildern: Ausrüstung, Ausbildung, Führung, Einsatz. Limburg/Lahn, Germany: C. A. Starke, 1974 François, Guy. Eisenbahnartillerie: Histoire de l'artillerie lourd sur voie ferrée allemande des origines à 1945. Paris: Editions Histoire et Fortifications, 2006 Gander and Chamberlain, Peter. Weapons of the Third Reich: An Encyclopedic Survey of All Small Arms and Special Weapons of the German Land Forces 1939–1945.

New York: Doubleday, 1979 ISBN 0-385-15090-3 Hogg, Ian V. German Artillery of World War Two. 2nd corrected edition. Mechanicsville, PA: Stackpole Books, 1997 ISBN 1-85367-480-X Kosar, Franz. Eisenbahngeschütz der Welt. Stuttgart: Motorbook, 1999 ISBN 3-613-01976-0