Audible free book: http://www.audible.com/computerphile
PostScript is more than just a 2D graphics language, it's a fully operational programming language Professor Brailsford explains how it works.

Reverse Polish Notation and the Stack:    • Reverse Polish Notation and The Stack...  

At 7min 15seconds the Professor refers to for as being the 'operand' when he meant the 'operator'.

The Professor's PS Program: http://bit.ly/postscriptprog

  / computerphile  
  / computer_phile  

This video was filmed and edited by Sean Riley.

Computer Science at the University of Nottingham: http://bit.ly/nottscomputer

Computerphile is a sister project to Brady Haran's Numberphile. See the full list of Brady's video projects at: http://bit.ly/bradychannels