In this era of invisible computing how do you define a computer? Professor Tom Rodden talks to Brady about what counts and what doesn't. EXTRA BITS: https://www.youtube.com/watch?v=xzYOx_gT4_w Mainframes and the Unix Revolution: https://www.youtube.com/watch?v=-rPPqm44xLs http://www.facebook.com/computerphile https://twitter.com/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