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Paged Memory
In computer operating systems, memory paging is a memory management scheme by which a computer stores and retrieves data from secondary storage for use in main memory. In this scheme, the operating system retrieves data from secondary storage in same-size blocks called ''pages''. Paging is an important part of virtual memory implementations in modern operating systems, using secondary storage to let programs exceed the size of available physical memory. For simplicity, main memory is called "RAM" (an acronym of random-access memory) and secondary storage is called "disk" (a shorthand for hard disk drive, drum memory or solid-state drive, etc.), but as with many aspects of computing, the concepts are independent of the technology used. Depending on the memory model, paged memory functionality is usually hardwired into a CPU/MCU by using a Memory Management Unit (MMU) or Memory Protection Unit (MPU) and separately enabled by privileged system code in the operating system's ker ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as Computer program, programs. These programs enable computers to perform a wide range of tasks. A computer system is a nominally complete computer that includes the Computer hardware, hardware, operating system (main software), and peripheral equipment needed and used for full operation. This term may also refer to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of Programmable logic controller, industrial and Consumer electronics, consumer products use computers as control systems. Simple special-purpose devices like microwave ovens and remote controls are included, as are factory devices like industrial robots and computer-aided design, as well as general-purpose devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Register
A control register is a processor register which changes or controls the general behavior of a CPU or other digital device. Common tasks performed by control registers include interrupt control, switching the addressing mode, paging control, and coprocessor control. Control registers in x86 series CR0 The CR0 register is 32 bits long on the 386 and higher processors. On x64 processors in long mode, it (and the other control registers) is 64 bits long. CR0 has various control flags that modify the basic operation of the processor. Register CR0 is the 32 Bit version of the old Machine Status Word (MSW) register. The MSW register was expanded to the Control Register with the appearance of the i386 processor. CR1 Reserved, the CPU will throw a # UD exception when trying to access it. CR2 Contains a value called Page Fault Linear Address (PFLA). When a page fault occurs, the address the program attempted to access is stored in the CR2 register. CR3 Used when virtual addr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM System/360 Model 40
The IBM System/360 Model 40 was a mid-range member of the IBM System/360 family. It was announced on April 7, 1964, shipped in 1965, and withdrawn on October 7, 1977. History On April 7, 1964, IBM announced the IBM System/360, to be available in six models. The 360/40 was first delivered in April 1965. The 360/30 and the 360/40 were the two largest revenue producing System/360 models, accounting for over half of the units sold. Models Five models of the 360/40 were offered. The D40, E40, F40, G40 and H40 were configured with 16K, 32K, 64K, 128K and 256K of core memory and correspondingly 16, 32, 64, 128 and 128 not a typo: the physical limit seemed to be 224; see p. 17 of the Model 30 Functional Characteristics multiplexer subchannels. The H40 occupied "more floor space than the other models." Configuration Microprogramming Like most System/360 models the Model 40 was microprogrammed. The microcode was stored in transformer read-only storage (TROS), organized as up ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley Timesharing System
The Berkeley Timesharing System was a pioneering time-sharing operating system implemented between 1964 and 1967 at the University of California, Berkeley. It was designed as part of Project Genie and marketed by Scientific Data Systems for the SDS 940 computer system. It was the first commercial time-sharing which allowed general-purpose user programming, including machine language. History In the mid-1960s, most computers used batch processing: one user at a time with no interactivity. A few pioneering systems such as the Atlas Supervisor at the University of Manchester, Compatible Time-Sharing System at MIT, and the Dartmouth Time Sharing System at Dartmouth College required large expensive machines. Implementation started in 1964 with the arrival of the SDS 930 which was modified slightly, and an operating system was written from scratch. Students who worked on the Berkeley Timesharing System included undergraduates Chuck Thacker and L. Peter Deutsch and doctoral student But ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM M44/44X
The IBM M44/44X was an experimental computer system from the mid-1960s, designed and operated at IBM's Thomas J. Watson Research Center at Yorktown Heights, New York. It was based on an IBM 7044 (the 'M44'), and simulated multiple 7044 virtual machines (the '44X'), using both hardware and software. Key team members were Dave Sayre and Rob Nelson. This was a groundbreaking machine, used to explore paging, the virtual machine concept, and computer performance measurement. It was purely a research system, and was cited in 1981 by Peter Denning as an outstanding example of experimental computer science. The term ''virtual machine'' probably originated with the M44/44X project, from which it was later appropriated by the CP-40 team to replace their earlier term ''pseudo machine''. Unlike CP-40 and later CP/CMS control programs, M44/44X did ''not'' implement a complete simulation of the underlying hardware (i.e. full virtualization). CP-40 project leader Robert Creasy observed: The M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Manchester
, mottoeng = Knowledge, Wisdom, Humanity , established = 2004 – University of Manchester Predecessor institutions: 1956 – UMIST (as university college; university 1994) 1904 – Victoria University of Manchester 1880 – Victoria University 1851 – Owens College 1824 – Manchester Mechanics' Institute , endowment = £242.2 million (2021) , budget = £1.10 billion (2020–21) , chancellor = Nazir Afzal (from August 2022) , head_label = President and vice-chancellor , head = Nancy Rothwell , academic_staff = 5,150 (2020) , total_staff = 12,920 (2021) , students = 40,485 (2021) , undergrad = () , postgrad = () , city = Manchester , country = England, United Kingdom , campus = Urban and suburban , colours = Manchester Purple Manchester Yellow , free_label = Scarf , free = , website = , logo = UniOfManchesterLogo.svg , affiliations = Universities Research Association Sutton 30 Russell Group EUA N8 Group NWUA ACUUniversities UK The Universit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlas Supervisor
The Atlas Supervisor was the program which managed the allocation of processing resources of Manchester University's Atlas Computer so that the machine was able to act on many tasks and user programs concurrently. Its various functions included running the Atlas computer's virtual memory (Atlas Supervisor paper, section 3, Store Organisation) and is ‘considered by many to be the first recognisable modern operating system’. Brinch Hansen Per Brinch Hansen (13 November 1938 – 31 July 2007) was a Danish-American computer scientist known for his work in operating systems, concurrent programming and parallel and distributed computing. Biography Early life and education Per B ... described it as "the most significant breakthrough in the history of operating systems." References ;Notes ;Bibliography * * External linksThe Atlas Supervisor paper (T Kilburn, R B Payne, D J Howarth, 1962) 1962 software Discontinued operating systems {{operating-system-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlas (computer)
The Atlas Computer was one of the world's first supercomputers, in use from 1962 (when it was claimed to be the most powerful computer in the world) to 1972. Atlas' capacity promoted the saying that when it went offline, half of the United Kingdom's computer capacity was lost. It is notable for being the first machine with virtual memory (at that time referred to as 'one-level store') using paging techniques; this approach quickly spread, and is now ubiquitous. Atlas was a second-generation computer, using discrete germanium transistors. Atlas was created in a joint development effort among the University of Manchester, Ferranti International plc and the Plessey Co., plc. Two other Atlas machines were built: one for British Petroleum and the University of London, and one for the Atlas Computer Laboratory at Chilton near Oxford. A derivative system was built by Ferranti for Cambridge University. Called the Titan, or Atlas 2, it had a different memory organisation and ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index. The firm was known for work in the area of power grid systems and defence electronics. In addition, in 1951 Ferranti began selling an early computer, the Ferranti Mark 1. The Belgian subsidiary lives on as Ferranti Computer Systems and as of 1994 is part of the Nijkerk Holding. History Beginnings Sebastian Ziani de Ferranti established his first business Ferranti, Thompson and Ince in 1882. The company developed the Ferranti-Thompson Alternator. Ferranti focused on alternating current power distribution early on, and was one of the few UK experts. To avoid confusion, he is often referred to as Dr Ferranti to distinguish him from the Ferranti company itself. In 1885 Dr Ferranti established a new business, with Francis Ince and Charles Sparks as partners, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fragmentation (computer)
In computer storage, fragmentation is a phenomenon in which storage space, main storage or secondary storage, is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. Basic principle When a computer program requests blocks of memory from the computer system, the blocks are allocated in chunks. When the computer program is finished with a chunk, it can free it back to the system, making it available to later be allocated again to another or the same program. The size and the amount of time a chunk is held by a program varies. During its lifespan, a computer program can request and free many chunks of memory. When a program is started, the free memory areas are long and contiguous. Over time and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Contiguous Data Storage
In computer storage, fragmentation is a phenomenon in which storage space, main storage or secondary storage, is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific system of storage allocation in use and the particular form of fragmentation. In many cases, fragmentation leads to storage space being "wasted", and in that case the term also refers to the wasted space itself. Basic principle When a computer program requests blocks of memory from the computer system, the blocks are allocated in chunks. When the computer program is finished with a chunk, it can free it back to the system, making it available to later be allocated again to another or the same program. The size and the amount of time a chunk is held by a program varies. During its lifespan, a computer program can request and free many chunks of memory. When a program is started, the free memory areas are long and contiguous. Over time and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
