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Hard Real-time System
Real-time computing (RTC) is the computer science term for hardware and software systems subject to a "real-time constraint", for example from event to system response. Real-time programs must guarantee response within specified time constraints, often referred to as "deadlines". Ben-Ari, Mordechai; "Principles of Concurrent and Distributed Programming", ch. 16, Prentice Hall, 1990, , page 164 Real-time responses are often understood to be in the order of milliseconds, and sometimes microseconds. A system not specified as operating in real time cannot usually ''guarantee'' a response within any timeframe, although ''typical'' or ''expected'' response times may be given. Real-time processing ''fails'' if not completed within a specified deadline relative to an event; deadlines must always be met, regardless of system load. A real-time system has been described as one which "controls an environment by receiving data, processing them, and returning the results sufficiently qui ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Real-time Communication
Real-time communication (RTC) is a category of software protocols and communication hardware media that gives real-time guarantees, which is necessary to support real-time guarantees of real-time computing.Sharad Sundaresan; Riccardo Bettati"Distributed Connection Management for Real-Time Communication over Wormhole-Routed Networks" 1997. Real-time communication protocols are dependent not only on the validity and integrity of data transferred but also the timeliness of the transfer. Real-time communication systems are generally understood as one of two types: ''Hard Real-Time (HRT)'' and ''Soft Real-Time (SRT)''. The difference between a hard and soft real-time communication system is the consequences of incorrect operation. Safety-critical systems capable of causing catastrophic consequences upon a fault, such as aircraft fly-by-wire systems, are designated as hard real-time, whereas non-critical but ideally real-time systems, such as hotel reservation systems, are designated a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simulation
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or process, whereas the simulation represents the evolution of the model over time. Often, computers are used to execute the computer simulation, simulation. Simulation is used in many contexts, such as simulation of technology for performance tuning or optimizing, safety engineering, testing, training, education, and video games. Simulation is also used with scientific modelling of natural systems or human systems to gain insight into their functioning, as in economics. Simulation can be used to show the eventual real effects of alternative conditions and courses of action. Simulation is also used when the real system cannot be engaged, because it may not be accessible, or it may be dangerous or unacceptable to engage, or it is being designed bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOS Technology 6502
The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small team led by Chuck Peddle for MOS Technology. The design team had formerly worked at Motorola on the Motorola 6800 project; the 6502 is essentially a simplified, less expensive and faster version of that design. When it was introduced in 1975, the 6502 was the least expensive microprocessor on the market by a considerable margin. It initially sold for less than one-sixth the cost of competing designs from larger companies, such as the 6800 or Intel 8080. Its introduction caused rapid decreases in pricing across the entire processor market. Along with the Zilog Z80, it sparked a series of projects that resulted in the home computer revolution of the early 1980s. Popular video game consoles and home computers of the 1980s and early 1990s, su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dumb Terminal
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades. Early terminals were inexpensive devices but very slow compared to punched cards or paper tape for input, yet as the technology improved and video displays were introduced, terminals pushed these older forms of interaction from the industry. A related development was time-sharing systems, which evolved in parallel and made up for any inefficiencies in the user's typing ability with the ability to support multiple users on the same machine, each at their own terminal or terminals. The function of a terminal is typically confined to transcription and input of data; a device with significant local, programmable data-processing capability may be called a "smart terminal" or fat client. A term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data General Business Basic
Data General Business Basic was a BASIC interpreter (based on a version from MAI Basic Four) marketed by Data General for their Nova minicomputer in the 1970s, and later ported to the Data General Eclipse MV and AViiON computers. Most business applications for the Nova were developed in Business Basic. Business Basic was an integer-only language inspired by COBOL, and contained powerful string-handling functions and the ability to manipulate indexed files very quickly. It also provided full control over the display screen, with cursor positioning, attribute setting, and region-blanking commands. Business Basic could interface to Data General's INFOS II database, and make calls directly to the operating system. A lock server gave multiple concurrent users efficient access to database records. Small business programs could be developed and debugged rapidly with Business Basic because of the interactive nature of the interpreter, but the language did not provide many structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-sharing
In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1 Its emergence as the prominent model of computing in the 1970s represented a major technological shift in the history of computing. By allowing many users to interact concurrently with a single computer, time-sharing dramatically lowered the cost of providing computing capability, made it possible for individuals and organizations to use a computer without owning one, and promoted the interactive use of computers and the development of new interactive applications. History Batch processing The earliest computers were extremely expensive devices, and very slow in comparison to later models. Machines were typically dedicated to a particular set of tasks and operated by control panels, the operator manually entering small programs via switches in order ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RT-11
RT-11 (Real-time 11) is a discontinued small, low-end, single-user real-time operating system for the full line of Digital Equipment Corporation PDP-11 16-bit computers. RT-11 was first implemented in 1970. It was widely used for real-time computing systems, process control, and data acquisition across all PDP-11s. It was also used for low-cost general-use computing. Features Multitasking RT-11 systems did not support preemptive multitasking, but most versions could run multiple simultaneous applications. All variants of the monitors provided a ''background job''. The FB, XM, and ZM monitors also provided a ''foreground job'', and six ''system jobs'' if selected via the SYSGEN system generation program. These tasks had fixed priorities, with the background job lowest and the foreground job highest. It was possible to switch between jobs from the system console user interface, and SYSGEN could generate a monitor that provided a single background job (the SB, XB and ZB variants). T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until forced to resign in 1992, after the company had gone into precipitous decline. The company produced many different product lines over its history. It is best known for the work in the minicomputer market starting in the mid-1960s. The company produced a series of machines known as the PDP line, with the PDP-8 and PDP-11 being among the most successful minis in history. Their success was only surpassed by another DEC product, the late-1970s VAX "supermini" systems that were designed to replace the PDP-11. Although a number of competitors had successfully competed with Digital through the 1970s, the VAX cemented the company's place as a leading vendor in the computer space. As microcomputers improved in the late 1980s, especially wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foreground-background
Foreground-background is a scheduling algorithm that is used to control an execution of multiple processes on a single processor. It is based on two waiting lists, the first one is called foreground because this is the one in which all processes initially enter, and the second one is called background because all processes, after using all of their execution time in foreground, are moved to background. When a process becomes ready it begins its execution in foreground immediately, forcing the processor to give up execution of the current process in the background and execute the newly created process for a predefined period. This period is usually 2 or more quanta. If the process is not finished after its execution in the foreground it is moved to background waiting list where it will be executed only when the foreground list is empty. After being moved to the background, the process is then run longer than before, usually 4 quanta. The time of execution is increased because the pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data General RDOS
The Data General RDOS (''Real-time Disk Operating System'') is a real-time operating system released in 1970. The software was bundled with the company's popular Nova and Eclipse minicomputers. Overview RDOS is capable of multitasking, with the ability to run up to 32 tasks (similar to the current term threads) simultaneously on each of two grounds ( foreground and background) within a 64 KB memory space. Later versions of RDOS are compatible with Data General's 16-bit Eclipse minicomputer line. A cut-down version of RDOS, without real-time background and foreground capability but still capable of running multiple threads and multi-user Data General Business Basic, is called Data General Diskette Operating System (DG-DOS or now—somewhat confusingly—simply DOS); another related operating system is RTOS, a Real-Time Operating System for diskless environments. RDOS on microNOVA-based "Micro Products" micro-minicomputers is sometimes called DG/RDOS. RDOS was supersede ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data General
Data General Corporation was one of the first minicomputer firms of the late 1960s. Three of the four founders were former employees of Digital Equipment Corporation (DEC). Their first product, 1969's Data General Nova, was a 16-bit minicomputer intended to both outperform and cost less than the equivalent from DEC, the 12-bit PDP-8. A basic Nova system cost or less than a similar PDP-8 while running faster, offering easy expandability, being significantly smaller, and proving more reliable in the field. Combined with Data General RDOS (DG/RDOS) and programming languages like Data General Business Basic, Novas provided a multi-user platform far ahead of many contemporary systems. A series of updated Nova machines were released through the early 1970s that kept the Nova line at the front of the 16-bit mini world. The Nova was followed by the Eclipse series which offered much larger memory capacity while still being able to run Nova code without modification. The Eclipse launch wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital On-screen Graphic
A digital on-screen graphic, digitally originated graphic (DOG, bug, or network bug) is a watermark-like station logo that most television broadcasters overlay over a portion of the screen area of their programs to identify the channel. They are thus a form of permanent visual station identification, increasing brand recognition and asserting ownership of the video signal. The graphic identifies the source of programming, even if it has been time-shifted—that is, recorded to videotape, DVD, or a digital personal video recorder such as TiVo. Many of these technologies allow viewers to skip or omit traditional between-programming station identification; thus the use of a DOG enables the station or network to enforce brand identification even when standard commercials are skipped. DOG watermarking helps to reduce off-the-air copyright infringement—for example, the distribution of a current series' episodes on DVD: the watermarked content is easily differentiated from "offic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
