Computer simulations discussed in physical terms and terminology
  As known, any numerical simulation is composed of two parts: (1) the initial part of writing the relevant code and (2) the running of this code on the computer screen. The second part of running the program is extensively discussed theoretically and technically in the relevant literature. In this work we pay special attention to the less discussed first part and show that it may be discussed in a terminology and notation which describe physical phenomena. As examples we discuss the two cases of simulating (1) the harmonic oscillator and (2) the electron-photon interaction which results in the known Lamb shift. 
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