Real-time computing (RTC) is the
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 (includi ...
term for
hardware and
software
Software is a set of computer programs and associated software documentation, documentation and data (computing), data. This is in contrast to Computer hardware, hardware, from which the system is built and which actually performs the work.
...
systems subject to a "real-time constraint", for example from
event
Event may refer to:
Gatherings of people
* Ceremony, an event of ritual significance, performed on a special occasion
* Convention (meeting), a gathering of individuals engaged in some common interest
* Event management, the organization of e ...
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 quickly to affect the environment at that time". The term "real-time" is also used in
simulation
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...
to mean that the simulation's clock runs at the same speed as a real clock, and in
process control and
enterprise system
Enterprise software, also known as enterprise application software (EAS), is computer software used to satisfy the needs of an organization rather than individual users. Such organizations include businesses, schools, interest-based user groups, ...
s to mean "without significant delay".
Real-time software may use one or more of the following:
synchronous programming language
A synchronous programming language is a computer programming language optimized for programming reactive systems. Computer systems can be sorted in three main classes: (1) transformational systems that take some inputs, process them, deliver their ...
s,
real-time operating system
A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...
s (RTOSes), and real-time networks, each of which provide essential frameworks on which to build a real-time software application.
Systems used for many
safety-critical
A safety-critical system (SCS) or life-critical system is a system whose failure or malfunction may result in one (or more) of the following outcomes:
* death or serious injury to people
* loss or severe damage to equipment/property
* environme ...
applications must be real-time, such as for control of
fly-by-wire
Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, and flight control ...
aircraft, or
anti-lock brakes
An anti-lock braking system (ABS) is a automobile safety, safety anti-Skid (automobile), skid Brake, braking system used on aircraft and on land motor vehicle, vehicles, such as cars, motorcycles, trucks, and buses. ABS operates by preventing t ...
, both of which demand immediate and accurate mechanical response.
History
The term ''real-time'' derives from its use in early
simulation
A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the s ...
, in which a real-world process is simulated at a rate that matched that of the real process (now called
real-time simulation
Real-time simulation refers to a computer model of a physical system that can execute at the same rate as actual "wall clock" time. In other words, the computer model runs at the same rate as the actual physical system. For example, if a tank tak ...
to avoid ambiguity).
Analog computer
An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (''analog signals'') to model the problem being solved. In ...
s, most often, were capable of simulating at a much faster pace than real-time, a situation that could be just as dangerous as a slow simulation if it were not also recognized and accounted for.
Minicomputers, particularly in the 1970s onwards, when built into dedicated
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...
s such as DOG (
Digital on-screen graphic) scanners, increased the need for low-latency priority-driven responses to important interactions with incoming data and so operating systems such as
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 minicompute ...
's
RDOS (Real-Time Disk Operating System) and RTOS with
background and foreground scheduling as well as
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 un ...
's
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 computin ...
date from this era. Background-foreground scheduling allowed low priority tasks CPU time when no foreground task needed to execute, and gave absolute priority within the foreground to threads/tasks with the highest priority. Real-time operating systems would also be used for
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 ...
multiuser duties. For example,
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 busines ...
could run in the foreground or background of RDOS and would introduce additional elements to the scheduling algorithm to make it more appropriate for people interacting via
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 a ...
s.
Once when the
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 te ...
(used in the
Commodore 64 and
Apple II), and later when the
Motorola 68000 (used in the
Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
,
Atari ST, and
Commodore Amiga
Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...
) were popular, anybody could use their home computer as a real-time system. The possibility to deactivate other interrupts allowed for hard-coded loops with defined timing, and the low
interrupt latency
In computing, interrupt latency refers to the delay between the start of an Interrupt Request (IRQ) and the start of the respective Interrupt Service Routine (ISR). For many operating systems, devices are serviced as soon as the device's interrup ...
allowed the implementation of a real-time operating system, giving the user interface and the disk drives lower priority than the real-time thread. Compared to these the
programmable interrupt controller of the Intel CPUs (8086..80586) generates a very large latency and the Windows operating system is neither a real-time operating system nor does it allow a program to take over the CPU completely and use its own
scheduler
A schedule or a timetable, as a basic time-management tool, consists of a list of times at which possible tasks, events, or actions are intended to take place, or of a sequence of events in the chronological order in which such things are i ...
, without using native machine language and thus surpassing all interrupting Windows code. However, several coding libraries exist which offer real time capabilities in a high level language on a variety of operating systems, for example
Java Real Time. The
Motorola 68000 and subsequent family members (68010, 68020 etc.) also became popular with manufacturers of industrial control systems. This application area is one in which real-time control offers genuine advantages in terms of process performance and safety.
Criteria for real-time computing
A system is said to be ''real-time'' if the total correctness of an operation depends not only upon its logical correctness, but also upon the time in which it is performed. Real-time systems, as well as their deadlines, are classified by the consequence of missing a deadline:
* ''Hard'' missing a deadline is a total system failure.
* ''Firm'' infrequent deadline misses are tolerable, but may degrade the system's quality of service. The usefulness of a result is zero after its deadline.
* ''Soft'' the usefulness of a result degrades after its deadline, thereby degrading the system's quality of service.
Thus, the goal of a ''hard real-time system'' is to ensure that all deadlines are met, but for ''soft real-time systems'' the goal becomes meeting a certain subset of deadlines in order to optimize some application-specific criteria. The particular criteria optimized depend on the application, but some typical examples include maximizing the number of deadlines met, minimizing the lateness of tasks and maximizing the number of high priority tasks meeting their deadlines.
Hard real-time systems are used when it is imperative that an event be reacted to within a strict deadline. Such strong guarantees are required of systems for which not reacting in a certain interval of time would cause great loss in some manner, especially damaging the surroundings physically or threatening human lives (although the strict definition is simply that missing the deadline constitutes failure of the system). Some examples of hard real-time systems:
* A
car engine
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.
Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
control system is a hard real-time system because a delayed signal may cause engine failure or damage.
* Medical systems such as heart
pacemakers. Even though a pacemaker's task is simple, because of the potential risk to human life, medical systems like these are typically required to undergo thorough testing and certification, which in turn requires hard real-time computing in order to offer provable guarantees that a failure is unlikely or impossible.
* Industrial process controllers, such as a machine on an
assembly line
An assembly line is a manufacturing process (often called a ''progressive assembly'') in which parts (usually interchangeable parts) are added as the semi-finished assembly moves from workstation to workstation where the parts are added in se ...
. If the machine is delayed, the item on the assembly line could pass beyond the reach of the machine (leaving the product untouched), or the machine or the product could be damaged by activating the robot at the wrong time. If the failure is detected, both cases would lead to the assembly line stopping, which slows production. If the failure is not detected, a product with a defect could make it through production, or could cause damage in later steps of production.
* Hard real-time systems are typically found interacting at a low level with physical hardware, in
embedded system
An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...
s. Early video game systems such as the
Atari 2600
The Atari 2600, initially branded as the Atari Video Computer System (Atari VCS) from its release until November 1982, is a home video game console developed and produced by Atari, Inc. Released in September 1977, it popularized microprocesso ...
and
Cinematronics vector graphics had hard real-time requirements because of the nature of the graphics and timing hardware.
*
Softmodems replace a hardware modem with software running on a computer's CPU. The software must run every few milliseconds to generate the next audio data to be output. If that data is late, the receiving modem will lose synchronization, causing a long interruption as synchronization is reestablished or causing the connection to be lost entirely.
* Many types of
printers
Printer may refer to:
Technology
* Printer (publishing), a person or a company
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer ( fl. c. 1940), Indian journalist and activist
* Jam ...
have hard real-time requirements, such as
inkjet
Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper and plastic substrates. Inkjet printers were the most commonly used type of printer in 2008, and range from small inexpens ...
s (the ink must be deposited at the correct time as the printhead crosses the page),
laser printer
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively-charged cylinder called a "drum" to ...
s (the laser must be activated at the right time as the beam scans across the rotating drum), and dot matrix and various types of
line printer
A line printer prints one entire line of text before advancing to another line. Most early line printers were
impact printers.
Line printers are mostly associated with unit record equipment and the early days of digital computing, but the ...
s (the impact mechanism must be activated at the right time as the print mechanism comes into alignment with the desired output). A failure in any of these would cause either missing output or misaligned output.
In the context of
multitasking systems the
scheduling policy
In computing, scheduling is the action of assigning ''resources'' to perform ''tasks''. The ''resources'' may be processors, network links or expansion cards. The ''tasks'' may be threads, processes or data flows.
The scheduling activity is ca ...
is normally priority driven (
pre-emptive schedulers). In some situations, these can guarantee hard real-time performance (for instance if the set of tasks and their priorities is known in advance). There are other hard real-time schedulers such as
rate-monotonic which is not common in general-purpose systems, as it requires additional information in order to schedule a task: namely a bound or worst-case estimate for how long the task must execute. Specific algorithms for scheduling such hard real-time tasks exist, such as
earliest deadline first, which, ignoring the overhead of
context switching, is sufficient for system loads of less than 100%. New overlay scheduling systems, such as an
adaptive partition scheduler assist in managing large systems with a mixture of hard real-time and non real-time applications.
Firm real-time systems are more nebulously defined, and some classifications do not include them, distinguishing only hard and soft real-time systems. Some examples of firm real-time systems:
* The assembly line machine described earlier as ''hard'' real-time could instead be considered ''firm'' real-time. A missed deadline still causes an error which needs to be dealt with: there might be machinery to mark a part as bad or eject it from the assembly line, or the assembly line could be stopped so an operator can correct the problem. However, as long as these errors are infrequent, they may be tolerated.
Soft real-time systems are typically used to solve issues of concurrent access and the need to keep a number of connected systems up-to-date through changing situations. Some examples of soft real-time systems:
* Software that maintains and updates the flight plans for commercial
airline
An airline is a company that provides air transport services for traveling passengers and freight. Airlines use aircraft to supply these services and may form partnerships or alliances with other airlines for codeshare agreements, in wh ...
rs. The flight plans must be kept reasonably current, but they can operate with the latency of a few seconds.
* Live audio-video systems are also usually soft real-time. A frame of audio that's played late may cause a brief audio glitch (and may cause all subsequent audio to be delayed correspondingly, causing a perception that the audio is being played slower than normal), but this may be better than the alternatives of continuing to play silence, static, a previous audio frame, or estimated data. A frame of video that's delayed typically causes even less disruption for viewers. The system can continue to operate and also recover in the future using workload prediction and reconfiguration methodologies.
* Similarly, video games are often soft real-time, particularly as they try to meet a target
frame rate. As the next image cannot be computed in advance, since it depends on inputs from the player, only a short time is available to perform all the computing needed to generate a frame of video before that frame must be displayed. If the deadline is missed, the game can continue at a lower frame rate; depending on the game, this may only affect its graphics (while the gameplay continues at normal speed), or the gameplay itself may be slowed down (which was common on older
third- and
fourth-generation consoles).
Real-time in digital signal processing
In a real-time
digital signal processing (DSP) process, the analyzed (input) and generated (output) samples can be processed (or generated) continuously in the time it takes to input and output the same set of samples ''independent'' of the processing delay.
[Kuo, Sen M.; Lee, Bob H.; and Tian, Wenshun; "Real-Time Digital Signal Processing: Implementations and Applications", Wiley, 2006, ]
Section 1.3.4: ''Real-Time Constraints''
It means that the processing delay must be bounded even if the processing continues for an unlimited time. That means that the
mean
There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value (magnitude and sign) of a given data set.
For a data set, the '' ari ...
processing time per sample, including
overhead, is no greater than the sampling period, which is the reciprocal of the
sampling rate
In signal processing, sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave to a sequence of "samples".
A sample is a value of the signal at a point in time and/or s ...
. This is the criterion whether the samples are grouped together in large segments and processed as blocks or are processed individually and whether there are long, short, or non-existent
input and output buffers.
Consider an
audio DSP example; if a process requires 2.01 seconds to
analyze,
synthesize, or process 2.00 seconds of sound, it is not real-time. However, if it takes 1.99 seconds, it is or can be made into a real-time DSP process.
A common life analogy is standing in a line or
queue __NOTOC__
Queue () may refer to:
* Queue area, or queue, a line or area where people wait for goods or services
Arts, entertainment, and media
*''ACM Queue'', a computer magazine
* ''The Queue'' (Sorokin novel), a 1983 novel by Russian author ...
waiting for the checkout in a grocery store. If the line asymptotically grows longer and longer without bound, the checkout process is not real-time. If the length of the line is bounded, customers are being "processed" and output as rapidly, on average, as they are being inputted then that process ''is'' real-time. The grocer might go out of business or must at least lose business if they cannot make their checkout process real-time; thus, it is fundamentally important that this process is real-time.
A signal processing algorithm that cannot keep up with the flow of input data with output falling farther and farther behind the input, is not real-time. But if the delay of the output (relative to the input) is bounded regarding a process that operates over an unlimited time, then that signal processing algorithm is real-time, even if the throughput delay may be very long.
Live vs. real-time
Real-time signal processing is necessary, but not sufficient in and of itself, for live signal processing such as what is required in
live event support
Live event support includes staging, scenery, mechanicals, sound, lighting, video, special effects, transport, packaging, communications, costume and makeup for live performance events including theater, music, dance, and opera. They all share th ...
. Live audio digital signal processing requires both real-time operation and a sufficient limit to throughput delay so as to be tolerable to performers using
stage monitor
A stage monitor system is a set of performer-facing loudspeakers called monitor speakers, stage monitors, floor monitors, wedges, or foldbacks on stage during live music performances in which a sound reinforcement system is used to amplify a p ...
s or
in-ear monitor
In-ear monitors (IEMs) are devices used by musicians, audio engineers and audiophiles to listen to music or to hear a personal mix of vocals and stage instrumentation for live performance or recording studio mixing. They are also used by telev ...
s and not noticeable as
lip sync error
Audio-to-video synchronization (AV synchronization, also known as lip sync, or by the lack of it: lip-sync error, lip flap) refers to the relative timing of audio (sound) and video (image) parts during creation, post-production (mixing), transmis ...
by the audience also directly watching the performers. Tolerable limits to latency for live, real-time processing is a subject of investigation and debate but is estimated to be between 6 and 20 milliseconds.
Real-time bidirectional
telecommunications delays of less than 300 ms ("round trip" or twice the unidirectional delay) are considered "acceptable" to avoid undesired "talk-over" in conversation.
Real-time and high-performance
Real-time computing is sometimes misunderstood to be
high-performance computing
High-performance computing (HPC) uses supercomputers and computer clusters to solve advanced computation problems.
Overview
HPC integrates systems administration (including network and security knowledge) and parallel programming into a mult ...
, but this is not an accurate classification.
For example, a massive
supercomputer executing a scientific simulation may offer impressive performance, yet it is not executing a real-time computation. Conversely, once the hardware and software for an anti-lock braking system have been designed to meet its required deadlines, no further performance gains are obligatory or even useful. Furthermore, if a network server is highly loaded with network traffic, its response time may be slower but will (in most cases) still succeed before it times out (hits its deadline). Hence, such a network server would not be considered a real-time system: temporal failures (delays, time-outs, etc.) are typically small and compartmentalized (limited in effect) but are not
catastrophic failures. In a real-time system, such as the
FTSE 100 Index, a slow-down beyond limits would often be considered catastrophic in its application context. The most important requirement of a real-time system is consistent output, not high throughput.
Some kinds of software, such as many
chess-playing programs, can fall into either category. For instance, a chess program designed to play in a tournament with a clock will need to decide on a move before a certain deadline or lose the game, and is therefore a real-time computation, but a chess program that is allowed to run indefinitely before moving is not. In both of these cases, however, high performance is desirable: the more work a tournament chess program can do in the allotted time, the better its moves will be, and the faster an unconstrained chess program runs, the sooner it will be able to move. This example also illustrates the essential difference between real-time computations and other computations: if the tournament chess program does not make a decision about its next move in its allotted time it loses the game—i.e., it fails as a real-time computation—while in the other scenario, meeting the deadline is assumed not to be necessary. High-performance is indicative of the amount of processing that is performed in a given amount of time, whereas real-time is the ability to get done with the processing to yield a useful output in the available time.
Near real-time
The term "near real-time" or "nearly real-time" (NRT), in
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
s and
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, refers to the time
delay introduced, by automated
data processing or
network
Network, networking and networked may refer to:
Science and technology
* Network theory, the study of graphs as a representation of relations between discrete objects
* Network science, an academic field that studies complex networks
Mathematics ...
transmission, between the occurrence of an event and the use of the processed data, such as for display or
feedback and control purposes. For example, a near-real-time display depicts an event or situation as it existed at the current time minus the processing time, as nearly the time of the live event.
The distinction between the terms "near real time" and "real time" is somewhat nebulous and must be defined for the situation at hand. The term implies that there are no significant delays.
In many cases, processing described as "real-time" would be more accurately described as "near real-time".
Near real-time also refers to delayed real-time transmission of voice and video. It allows playing video images, in approximately real-time, without having to wait for an entire large video file to download. Incompatible databases can export/import to common flat files that the other database can import/export on a scheduled basis so that they can sync/share common data in "near real-time" with each other.
The distinction between "near real-time" and "real-time" varies, and the delay is dependent on the type and speed of the transmission. The delay in near real-time is typically in a range of 1-10 seconds.
Design methods
Several methods exist to aid the design of real-time systems, an example of which is
MASCOT
A mascot is any human, animal, or object thought to bring luck, or anything used to represent a group with a common public identity, such as a school, professional sports team, society, military unit, or brand name. Mascots are also used as fi ...
, an old but very successful method which represents the
concurrent
Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to:
Law
* Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea''
* Concurring opinion (also called a "concurrence"), a ...
structure of the system. Other examples are
HOOD
Hood may refer to:
Covering
Apparel
* Hood (headgear), type of head covering
** Article of academic dress
** Bondage hood, sex toy
* Hoodie, hooded sweatshirt
Anatomy
* Clitoral hood, a hood of skin surrounding the clitoris
* Hood, a flap of ...
, Real-Time UML,
AADL, the
Ravenscar profile The Ravenscar profile is a subset of the Ada tasking features designed for safety-critical hard real-time computing. It was defined by a separate technical report in Ada 95; it is now part of the Ada 2012 Standard. It has been named after the Englis ...
, and
Real-Time Java.
See also
*
Autonomous peripheral operation
In computing, autonomous peripheral operation is a hardware feature found in some microcontroller architectures to off-load certain tasks into embedded autonomous peripherals in order to minimize latencies and improve throughput in hard real-tim ...
*
Control system
*
Failure detector
*
Nodal architecture
*
Processing modes
*
Ptolemy Project
*
Real-time data Real-time data (RTD) is information that is delivered immediately after collection. There is no delay in the timeliness of the information provided. Real-time data is often used for navigation or tracking. Such data is usually processed using real- ...
*
Real-time computer graphics
Real-time computer graphics or real-time rendering is the sub-field of computer graphics focused on producing and analyzing images in real time. The term can refer to anything from rendering an application's graphical user interface (GUI) to ...
*
Real-time operating system
A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...
*
Real-time testing
*
Remote diagnostics
Remote diagnostics is the act of diagnosing a given symptom, issue or problem from a distance. Instead of the subject being co-located with the person or system done diagnostics, with remote diagnostics the subjects can be separated by physical di ...
*
Scheduling analysis real-time systems
*
Synchronous programming language
A synchronous programming language is a computer programming language optimized for programming reactive systems. Computer systems can be sorted in three main classes: (1) transformational systems that take some inputs, process them, deliver their ...
*
Time-utility function A Time/Utility Function (''TUF''), née ''Time/Value Function'', specifies the application-specific ''utility'' that an ''action'' (e.g., computational task, mechanical movement) yields depending on its completion time. TUFs and their utility interp ...
*
Ward–Mellor method
*
Worst-case execution time The worst-case execution time (WCET) of a computational task is the maximum length of time the task could take to execute on a specific hardware platform.
What it is used for
Worst case execution time is typically used in reliable real-time sys ...
References
Further reading
*
*.
*.
The International Journal of Time-Critical Computing Systems*
External links
IEEE Technical Committee on Real-Time SystemsEuromicro Technical Committee on Real-time SystemsThe What, Where and Why of Real-Time Simulation*
{{DEFAULTSORT:Real-Time Computing
*