Conservation of Information
Information can not be created or destroyed by code. It can only be lost.
Information can only be created by a User or a Sensor. The closest a computer can get to creating information is with pseudo-random values, which only appear to be new Information. True random values require a sensor, like a chip which monitors radio-active decay. The second clause, that Information can not be destroyed, is based on the realization that stateful Information, once mutated, does not change the reality of the Information that was received. A computer can alter state, resulting in the loss of Information, but Information exists separate from mutation.
See Rich Hickey "Information is facts, and facts don't change." From his talk Value of Values (paraphrasing).