Mlnimum-cost encoding of information

Haying determined a cost in energy, time, or money of transmitting each of a set of symbols (e.g., dot and dash, pulses of various amplitudes, etc.), one may inquire as to the nature of a code using these symbols which will transmit a given amount of information at the least cost, or will transmit information at a given rate for the least cost per unit time. Such a code must use each symbol with a relative frequency given by a negative exponential of a linear combination of its cost and duration in the case of a noiseless communication channel. If noise is present, the cost of each symbol is effectively increased by a multiple of its "prevarication," i.e., the entropy of the received symbol when only the given symbol is transmitted.