"Capabilities of digital computers.

The capabilities of a digital computer can best be presented by means
of an analogy between hand computation and the functions performed by
the parts of a digital computer. A general rule for evaluating the
capabilities of a digital computer is: If the steps in the solution
to a problem can be broken down into sequences of unambiguous
instructions that could conceptually be performed by a very patient
secretary who has no knowledge of the subject matter but who has
infinite perseverance and can follow instructions precisely, never
making an error, then the problem can be solved on a digital computer.
This rule is an oversimplification only insofar as the necessary
computation time on the computer and the cost of this time are also
restrictions."


Report on the use of computers in biology and medicine
By Robert Steven Ledley,
National Research Council (U.S.)
1960
Page 47