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Persistent Storage
In computer science, persistence refers to the characteristic of state of a system that outlives (persists more than) the process that created it. This is achieved in practice by storing the state as data in computer data storage. Programs have to transfer data to and from storage devices and have to provide mappings from the native programming-language data structures to the storage device data structures. Picture editing programs or word processors, for example, achieve state persistence by saving their documents to files. Orthogonal or transparent persistence Persistence is said to be "orthogonal" or "transparent" when it is implemented as an intrinsic property of the execution environment of a program. An orthogonal persistence environment does not require any specific actions by programs running in it to retrieve or save their state. Non-orthogonal persistence requires data to be written and read to and from storage using specific instructions in a program, resulting i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (including the design and implementation of hardware and software). Computer science is generally considered an area of academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing security vulnerabilities. Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of repositories ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journaling File System
A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a " journal", which is usually a circular log. In the event of a system crash or power failure, such file systems can be brought back online more quickly with a lower likelihood of becoming corrupted. Depending on the actual implementation, a journaling file system may only keep track of stored metadata, resulting in improved performance at the expense of increased possibility for data corruption. Alternatively, a journaling file system may track both stored data and related metadata, while some implementations allow selectable behavior in this regard. History In 1990 IBM introduced JFS in AIX 3.1 as one of the first UNIX commercial filesystems that implemented journaling. The next year the idea was popularized in a widely cited paper on log-structured file systems. This was subsequent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-level Store
Single-level storage (SLS) or single-level memory is a computer storage term which has had two meanings. The two meanings are related in that in both, pages of memory may be in primary storage ( RAM) or in secondary storage (disk), and that the physical location of a page is unimportant to a process. The term originally referred to what is now usually called virtual memory, which was introduced in 1962 by the Atlas system at the University of Manchester. In modern usage, the term usually refers to the organization of a computing system in which there are no files, only persistent objects (sometimes called segments), which are mapped into processes' address spaces (which consist entirely of a collection of mapped objects). The entire storage of the computer is thought of as a single two-dimensional plane of addresses (segment, and address within segment). The persistent object concept was first introduced by Multics in the mid-1960s, in a project shared by MIT, General Elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multics
Multics ("Multiplexed Information and Computing Service") is an influential early time-sharing operating system based on the concept of a single-level memory.Dennis M. Ritchie, "The Evolution of the Unix Time-sharing System", Communications of the ACM, Vol. 17, 1984, pp. 365-375. Nathan Gregory writes that Multics "has influenced all modern operating systems since, from microcomputers to mainframes." Initial planning and development for Multics started in 1964, in Cambridge, Massachusetts. Originally it was a cooperative project led by MIT ( Project MAC with Fernando Corbató) along with General Electric and Bell Labs. It was developed on the GE 645 computer, which was specially designed for it; the first one was delivered to MIT in January 1967. GE offered their earlier 635 systems with an early timesharing system known as "Mark I" and intended to offer the 645 with Multics as a larger successor. Bell withdrew from the project in 1969 as it became clear it would not deliver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CapROS
Capability-based Reliable Operating System (CapROS) is an operating system incorporating pure capability-based security. It features automatic persistence of data and processes, even across system reboots. Capability systems naturally support the principle of least authority, which improves security and fault tolerance. It is free and open-source software released under the GNU General Public License version 2 (GPLv2), and GNU Lesser General Public License version 2 (LGPLv2). CapROS is an evolution of the Extremely Reliable Operating System (EROS). While EROS was purely a research system, CapROS is intended to be a stable system of commercial quality. CapROS currently runs on Intel IA-32 and ARM microprocessors. CapROS is being developed by Strawberry Development Group with funding from the Defense Advanced Research Projects Agency (DARPA) and others. The primary developer is Charles Landau. History The CapROS project was formed in 2005 as a non-academic continuation of EROS ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extremely Reliable Operating System
Extremely Reliable Operating System (EROS) is an operating system developed starting in 1991 at the University of Pennsylvania, and then Johns Hopkins University, and The EROS Group, LLC. Features include automatic data and process persistence, some preliminary real-time support, and capability-based security. EROS is purely a research operating system, and was never deployed in real world use. , development stopped in favor of a successor system, CapROS. Key concepts The overriding goal of the EROS system (and its relatives) is to provide strong support at the operating system level for the efficient restructuring of critical applications into small communicating components. Each component can communicate with the others only through protected interfaces, and is isolated from the rest of the system. A ''protected interface'', in this context, is one that is enforced by the lowest level part of the operating system, the kernel. That is the only part of the system that can move in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KeyKOS
KeyKOS is a persistent, pure capability-based operating system for the IBM S/370 mainframe computers. It allows emulating the environments of VM, MVS, and Portable Operating System Interface (POSIX). It is a predecessor of the Extremely Reliable Operating System (EROS), and its successor operating systems, CapROS, and Coyotos. KeyKOS is a nanokernel-based operating system. In the mid-1970s, development of KeyKOS began at Tymshare, Inc., under the name GNOSIS. In 1984, McDonnell Douglas McDonnell Douglas was a major American aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own merger with Boeing in 1997, it ... (MD) bought Tymshare. A year later MD spun off Key Logic, which bought GNOSIS and renamed it ''KeyKOS''. References External links * , Norman Hardy GNOSIS: A Prototype Operating System for the 1990s a 1979 paper, Tymshare Inc. a 1988 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for efficient use of the system and may also include accounting software for cost allocation of Scheduling (computing), processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of aroun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DBMS
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance. A database management system (DBMS) is the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS software additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an applicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random-access Memory
Random-access memory (RAM; ) is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory, in contrast with other direct-access data storage media (such as hard disks, CD-RWs, DVD-RWs and the older magnetic tapes and drum memory), where the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement. RAM contains multiplexing and demultiplexing circuitry, to connect the data lines to the addressed storage for reading or writing the entry. Usually more than one bit of storage is accessed by the same address, and RAM devices often have multiple data lines and are said to be "8-bit" or "16-bit", etc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Layer (object-oriented Design)
In software object-oriented design, a layer is a group of classes that have the same set of link-time module dependencies to other modules. In other words, a layer is a group of reusable components that are reusable in similar circumstances. In programming languages, the layer distinction is often expressed as "import" dependencies between software modules. Layers are often arranged in a tree-form hierarchy, with dependency relationships as links between the layers. Dependency relationships between layers are often either inheritance, composition or aggregation relationships, but other kinds of dependencies can also be used. Layers is an architectural pattern described in many books, for example ''Pattern-Oriented Software Architecture'' [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
