Programming 101–2. computing machine
Disclaimer: the Programming 101 series was originally written to be published as a short book. However, since I never got round to finishing it, I’m publishing the chapters here as individual blog posts…
The computing machine
So let’s start with the most basic question: “What is a computer program?” And perhaps we need to go even further back and ask “What is a
computer?”
Alan Turing and computability
The best place to start answering these questions is the notion of the
“computing machine” as proposed by Alan Turing (1912–1954), a British
mathematician who is widely considered to be the father of computer
science. Turing formalized the concepts of algorithm and computation by
describing the so-called Turing machine, which can be considered a model
of a general-purpose computer.
Turing first described his “computing” machine in 1936 with a strictly
mathematical purpose. Turing was looking for a way to prove that while
it is possible to formulate a procedure to produce all rational numbers
— — numbers that can be expressed as a fraction, e.g. 1 (1/1), 0.5 (1/2)
or 0.333… (1/3) — — , it is *not*…
