Virtual ICT1301

A 3D simulation of the ICT 1301 computer

Find Out More Run Virtual Flossie

What is an ICT 1301 computer?

The ICT 1301 was a British built and designed, second-generation computer (one which marks the move from valve/vacuum tube technology to transistors).

Around 180 of these computers were built by International Computers and Tabulators in the early 1960s. This machine used Germanium transistors and was relatively popular due to it being designed to be used with standard three-phase power, not have the requirements for a purpose built air-conditioned room and the ability to calculate in Sterling (Pounds, Shillings and Pence).

This website has an online simulation of the ICT 1301 computer, specifically serial number 6 which has been given the name "Flossie". This machine is currently located at The National Museum of Computing (in storage). It is one of only three remaining in the world, and the only one likely to ever be able to be restored to working status.

ICT 1301 Hardware ICT 1301 Software How do I use the simulation?
What does it do?
Credits and Links


A number of people I need to say thanks and tip my hat to... .. The National Museum of Computing where my obsession was sparked! Make sure you find time to see their rebuilt and fully working Bombe and Enigma demonstrations at the museum but also so much more including Colossus and the galleries on the breaking of Lorenz, the WITCH & EDSAC, Elliott 308 and all manner of home computers you can use. .. The ICT 1301 Resurrection Project. Bringing Computing History back to Life.
Flossie, is currently the oldest original 2nd Generation Electronic Stored Program Computer in the UK and these chaps have not only been hard at work trying to restore her, but have documentation and stories galore! This project wouldn't have been possible without their help!

3D software

A couple of amazing (and free to use) tools which enabled me to write Virtual Enigma

three.js is a cross-browser JavaScript library for creating 3D computer graphics in a web browser and an amazing piece of work. A big thank you to Mr.Doob for creating this wonder! a free and open source 3D creation suite which was used to create the models.


Creative Commons Licence
Virtual Enigma by is licensed under a Creative Commons Attribution 4.0 International License.

Please feel free to use Virtual ICT 1301 to learn about the ICT 1301 machine. If you find it useful or if you have any feedback or ideas for making it easier to use or understand, please do let me know.

It takes a long time to research and build these simulations and I love to hear about them being used, whether for your own information or in a classroom for STEM. Do please drop me a line to let me know if you do!

Let me know what you think!

Have I got something wrong, it doesn't work quite correctly on your computer or maybe you just want to say hi - find me on Twitter or check my Facebook or Twitter pages

Martin Gillow