We solve three problems of the Post Correspondence Problem, as found in Michael Sipser's "Introduction to the Theory of Computation".

## Closeness of Regular Languages – A Cool Proof

A proof of the closeness of the Regular Languages operations of Union, Concatenation, Star.

## Turing Machine Exercises

Solutions to some basic Turing Machine problems.

## Turing Machine Variants

Various variants of the Turing Machine. This is a quick reference of the most popular ones.