In the computer sciences the theories and proposals that have been put forward are of a quite different nature than the logical and mathematical ones, although they do inspire one another. The problem one faces here is precisely to set up a translation from a classical geometrical, analogous model to a model whereof the domain (usually) consists of the finite set of pixels or cells that make up the (computer) screen. The obvious drawback (from the perspective of this entry) is that nearly all these models assume the classical (infinite) model in the background and, hence, do not have a proper foundation of their own—a situation quite analogous to numerical analysis that relies on classical analysis for proving the correctness of the procedures. Most attention is paid to the problem of proving correspondences between the original and the discrete model to make sure that the image obtained is, in certain respects, faithful to the original. A simple mathematical example concerns the number of holes in a 3-dimensional Euclidean surface. One wants to be sure that every hole that shows up in the digital picture does indeed correspond to a hole in the original mathematical object. See Borwein &amp; Devlin (2009) for more examples. However, that being said, there is some work being done that does not want to rely on the classical continuous background but instead looks for “proper” axiomatisations and/or formalisations of a pixel geometry. See Kulpa (1979) and, more recently, Danielsson (2002) for some nice examples.