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ARX (operating System)
ARX was an unreleased Mach-like operating system written in Modula-2+ developed by Acorn Computers Ltd in the Acorn Research Centre (ARC) United Kingdom (UK) and later by Olivetti - which purchased Acorn - for Acorn's new Archimedes personal computers based on the ARM architecture reduced instruction set computer (RISC) central processing unit (CPUs). Overview According to the project Application ManagerTOP3 smart moves Richard Cownie. Real World Technologies (September 2009) Richard Cownie, during the project, while Acorn was developing the kernel, it used the C and Acorn Modula Execution Library (CAMEL) in the Acorn Extended Modula-2 (AEM2) compiler (ported from |
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archimedes. Acorn's computer dominated the UK educational computer market during the 1980s. Though the company was acquired and largely dismantled in early 1999, with various activities being dispersed amongst new and established companies, its legacy includes the development of reduced instruction set computing (RISC) personal computers. One of its operating systems, , continues to be developed by RISC OS Open. Some activities established by Acorn lived on: technology developed by Arm (company), Arm, created by Acorn as a joint venture with Apple, Inc., Apple and VLSI Technology, VLSI in 1990, is dominant in the mobile phone and personal digital assistant (PDA) microprocessor market. Acorn is sometimes referred to as the "British Apple" and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modula-2
Modula-2 is a structured, procedural programming language developed between 1977 and 1985/8 by Niklaus Wirth at ETH Zurich. It was created as the language for the operating system and application software of the Lilith personal workstation. It was later used for programming outside the context of the Lilith. Wirth viewed Modula-2 as a successor to his earlier programming languages Pascal and Modula. The main concepts are: # The module as a compiling unit for separate compiling # The coroutine as the basic building block for concurrent processes # Types and procedures that allow access to machine-specific data The language design was influenced by the Mesa language and the Xerox Alto, both from Xerox PARC, that Wirth saw during his 1976 sabbatical year there. Page 4. The computer magazine ''Byte'' devoted the August 1984 issue to the language and its surrounding environment. Modula-2 was followed by Modula-3, and later by the Oberon series of languages. Description Modula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User Interface
In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, while the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls and process controls. The design considerations applicable when creating user interfaces are related to, or involve such disciplines as, ergonomics and psychology. Generally, the goal of user interface design is to produce a user interface that makes it easy, efficient, and enjoyable (user-friendly) to operate a machine in the way which produces the desired result (i.e. maximum usability). This generally means that the operator needs to provide minimal input ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write Once Read Many
Write once read many (WORM) describes a data storage device in which information, once written, cannot be modified. This write protection affords the assurance that the data cannot be tampered with once it is written to the device, excluding the possibility of data loss from human error or malware. On ordinary (non-WORM) data storage devices, the number of times data can be modified is limited only by the lifespan of the device, as modification involves physical changes that may cause wear to the device. The "read many" aspect is unremarkable, as modern storage devices permit unlimited reading of data once written.Historical exceptions include time-limited discs such as Flexplay, designed for short-term rental of movies; and early non-volatile memory technologies such as magnetic-core memory and bubble memory, from which reading data also erased it. WORM protects the important files by keeping them safe and intact. It ensures the highest level of integrity and data security by e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lock (computer Science)
In computer science, a lock or mutex (from mutual exclusion) is a synchronization primitive: a mechanism that enforces limits on access to a resource when there are many threads of execution. A lock is designed to enforce a mutual exclusion concurrency control policy, and with a variety of possible methods there exists multiple unique implementations for different applications. Types Generally, locks are ''advisory locks'', where each thread cooperates by acquiring the lock before accessing the corresponding data. Some systems also implement ''mandatory locks'', where attempting unauthorized access to a locked resource will force an exception in the entity attempting to make the access. The simplest type of lock is a binary semaphore. It provides exclusive access to the locked data. Other schemes also provide shared access for reading data. Other widely implemented access modes are exclusive, intend-to-exclude and intend-to-upgrade. Another way to classify locks is by what hap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protection Ring
In computer science, hierarchical protection domains, often called protection rings, are mechanisms to protect data and functionality from faults (by improving fault tolerance) and malicious behavior (by providing computer security). Computer operating systems provide different levels of access to resources. A protection ring is one of two or more hierarchical ''levels'' or ''layers'' of privilege within the architecture of a computer system. This is generally hardware-enforced by some CPU architectures that provide different CPU modes at the hardware or microcode level. Rings are arranged in a hierarchy from most privileged (most trusted, usually numbered zero) to least privileged (least trusted, usually with the highest ring number). Ring 0 is the level with the most privileges and allows direct interaction with the physical hardware such as certain CPU functionality and chips on the motherboard. Special call gates between rings are provided to allow an outer ring to acces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User Space
A modern computer operating system usually segregates virtual memory into user space and kernel space. Primarily, this separation serves to provide memory protection and hardware protection from malicious or errant software behaviour. Kernel space is strictly reserved for running a privileged operating system kernel, kernel extensions, and most device drivers. In contrast, user space is the memory area where application software and some drivers execute. Overview The term user space (or userland) refers to all code that runs outside the operating system's kernel. User space usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output, manipulates file system objects, application software, etc. Each user space process normally runs in its own virtual memory space, and, unless explicitly allowed, cannot access the memory of other processes. This is the basis for memory protection in today' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thread (computing)
In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. The implementation of threads and processes differs between operating systems. In Modern Operating Systems, Tanenbaum shows that many distinct models of process organization are possible.TANENBAUM, Andrew S. Modern Operating Systems. 1992. Prentice-Hall International Editions, ISBN 0-13-595752-4. In many cases, a thread is a component of a process. The multiple threads of a given process may be executed concurrently (via multithreading capabilities), sharing resources such as memory, while different processes do not share these resources. In particular, the threads of a process share its executable code and the values of its dynamically allocated variables and non- thread-local global variables at any given time. History Threads made an early appearance under the name of "tasks ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Multitasking
In computing, multitasking is the concurrent execution of multiple tasks (also known as processes) over a certain period of time. New tasks can interrupt already started ones before they finish, instead of waiting for them to end. As a result, a computer executes segments of multiple tasks in an interleaved manner, while the tasks share common processing resources such as central processing units (CPUs) and main memory. Multitasking automatically interrupts the running program, saving its state (partial results, memory contents and computer register contents) and loading the saved state of another program and transferring control to it. This " context switch" may be initiated at fixed time intervals (pre-emptive multitasking), or the running program may be coded to signal to the supervisory software when it can be interrupted (cooperative multitasking). Multitasking does not require parallel execution of multiple tasks at exactly the same time; instead, it allows more than o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preemption (computing)
In computing, preemption is the act of temporarily interrupting an executing task, with the intention of resuming it at a later time. This interrupt is done by an external scheduler with no assistance or cooperation from the task. This preemptive scheduler usually runs in the most privileged protection ring, meaning that interruption and resuming are considered highly secure actions. Such a change in the currently executing task of a processor is known as context switching. User mode and kernel mode In any given system design, some operations performed by the system may not be preemptable. This usually applies to kernel functions and service interrupts which, if not permitted to run to completion, would tend to produce race conditions resulting in deadlock. Barring the scheduler from preempting tasks while they are processing kernel functions simplifies the kernel design at the expense of system responsiveness. The distinction between user mode and kernel mode, which det ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modula-3
Modula-3 is a programming language conceived as a successor to an upgraded version of Modula-2 known as Modula-2+. While it has been influential in research circles (influencing the designs of languages such as Java, C#, and Python) it has not been adopted widely in industry. It was designed by Luca Cardelli, James Donahue, Lucille Glassman, Mick Jordan (before at the Olivetti Software Technology Laboratory), Bill Kalsow and Greg Nelson at the Digital Equipment Corporation (DEC) Systems Research Center (SRC) and the Olivetti Research Center (ORC) in the late 1980s. Modula-3's main features are simplicity and safety while preserving the power of a systems-programming language. Modula-3 aimed to continue the Pascal tradition of type safety, while introducing new constructs for practical real-world programming. In particular Modula-3 added support for generic programming (similar to templates), multithreading, exception handling, garbage collection, object-oriented programming, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NeWS
News is information about current events. This may be provided through many different Media (communication), media: word of mouth, printing, Mail, postal systems, broadcasting, Telecommunications, electronic communication, or through the testimony of Witness, observers and witnesses to events. News is sometimes called "hard news" to differentiate it from soft media. Common topics for news reports include war, government, politics, education, health, the Climate change, environment, economy, business, fashion, entertainment, and sport, as well as Wikipedia:Unusual articles, quirky or unusual events. Government proclamations, concerning Monarchy, royal ceremonies, Law, laws, Tax, taxes, public health, and Crime, criminals, have been dubbed news since ancient times. Technology, Technological and Social change, social developments, often driven by government communication and espionage networks, have increased the speed with which news can spread, as well as influenced its conten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
