The vast majority of our mechanisms are viewed as analogue devices whose behaviour is over a large range a continuous function of all parameters involved: if we press the point of the pencil a little bit harder, we get a slightly thicker line, if the violinist slightly misplaces his finger, he plays slightly out of tune.

To the extent that we view ourselves as mechanisms, we view ourselves primarily as analogue devices: if we push a little harder we expect to do a little better.

Very often the behaviour is not only a continuous but even a monotonic function: to test whether a hammer suits us over a certain range of nails, we try it out on the smallest and largest nails of the range, and if the outcomes of those two experiments are positive, we are perfectly willing to believe that the hammer will suit us for all nails in between.

It is possible, and even tempting, to view a program as an abstract mechanism, as a device of some sort. To do so, however, is highly dangerous: the analogy is too shallow because a program is, as a mechanism, totally different from all the familiar analogue devices we grew up with. Like all digitally encoded information, it has unavoidably the uncomfortable property that the smallest possible perturbations —i.e. changes of a single bit— can have the most drastic consequences.

University of Texas in Austin

On the Cruelty of Really Teaching Computing Science

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But computers are digital and so small changes do not go hand in hand with small effects