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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 takes 10 minutes to fill in the real-world, the simulation would take 10 minutes as well.
Real-time simulation occurs commonly in computer gaming, but also is important in the industrial market for operator training and off-line controller tuning. Computer languages like LabVIEW, VisSim and Simulink allow quick creation of such real-time simulations and have connections to industrial displays and Programmable Logic Controllers via OLE for process control or digital and analog I/O cards. Several real-time simulator are available on the market like xPC Target and RT-LAB for mechatronic systems and using Simulink, eFPGAsim and eDRIVEsim for power electronic simulation and eMEGAsim, HYPERSIM and RTDS for power grid real-time (RTS) simulation.
What is real-time simulation
In a real time simulation the simulation is performed in a discrete time with constant step also known as fixed step simulation as time moves forward in equal duration of time, other techniques having variable step are used for high frequency transients but are unsuitable for real time simulation. In a real time simulation the time required to solve the internal state equations and functions representing the system must be less than the fixed step. If calculation time exceeds the time of the fixed step, an over run is said to have occurred. In simple words, real-time simulation must produce the internal variables and output within the same length of time as its physical counterpart would.
Configuring models to run in real time enables you to use hardware-in-the-loop simulation to test controllers. You can make design changes earlier in the development process, reducing costs and shortening the design cycle.
Real-time simulation in academic curricula
Real-time simulators are used extensively in many engineering fields. As a consequence, the inclusion of simulation applications in academic curricula can provide great value to the student. Statistical power grid protection tests, aircraft design and simulation, motor drive controller design methods and space robot integration are a few examples of real-time simulator technology applications. 
Real-time simulation as a literary method
Simulated Real Time is a literary method of creating an event with the help of authentic material accompanied by a commentary framework. By publishing documents (letters, diaries, official reports etc.) on the date on which they were written but a specified number of years later, an event can be reconstructed with exactly the same duration as when it first took place. The aim of this method is to gain greater understanding of an historical event in this way, using modern technology to bring it to life as vividly as possible. The method is giving an important contribution to contemporary Remembrance Culture, in a time where the survivors of the Holocaust are getting fewer.