Introduction
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The concept of "Computability" is a remarkably recent
concept within mathematics (circa 1920's). The power of the
idea lies partly in the fact that some well defined
operations in mathematics are NOT actually computable (such
as the halting of a Turing machine).  Computability is a
genuine "absolute" mathematical concept, and is beyond any
realisation, digital computing, analog, etc. The first
expression of computability is due to Alonzo Church and his
Lambda Calculus. 

In the following material we have, what I hope is, a gentle
introduction to Lambda Calculus. We will show that we can
express Boolean Algebra in L-calc, and the natural numbers.
This is only scratching the surface.