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the virtual data center - a working 1401 3D simulation

the virtual data center
a fully working walkable
1401 3D simulation - for free  


last updates: web site 2021-10-12  (minor updates 2021-10-20);  program v0.2.15  2021-10-15  (see changelog)

- questions or suggestions? have a look here: 1401 VDC Discord Server
- for up-to-date bug alerts see channel #bugs-and-fixes on discord

you are a beginner in respect of the 1401? see the youtube videos and books mentioned below.


2021-10-16 - new: APPLE MAC version available !     v0.2.15   download page

2021-10-15 - v0.2.15 - now with 1407 terminal !    download page  changelog   1407 info

- load card tool (tiny assembler): see tools
- address calculation tool: see tools


A working 3D simulation using the Unreal® Engine, exhibiting a 60's datacenter, imitating the historic IBM® 1401 mainframe.

Get your own 1401 feeling at home! Download see below.
This simulation assumes that you know what a punched card is.

The simulator tries to revive the original mainframe experience.
This includes the effort it took to achieve a desired result.
You are missing a program editor? Yes, those were the days!
You want to enter a program or some data? Go and punch some cards!
You have a typo in your card? Too bad!
Back in the days you might have been lucky if you had the system for one hour a day to test your programs.


A bunch of my videos, showcasing the datacenter simulator and general 1401 programming.

YouTube "rolffson's IBM 1401 channel"
IBM 1401 - let's program, #8: calculating prime numbers (feat. a video from Ken Shirriff)
IBM 1401 - let's program, #7: testing a program from the CHM 1401 team
IBM 1401 - let's program, #6: reading the IBM 729 tape drive
IBM 1401 - let's program, #4: load a program from card (printing "Hello World")

see about how to unlock the punch card import / export feature.

see for a quick download, installation and use walkthrough video for the simulator.

There are more videos form other authors, e.g. the CHM team and curiousmarc, simply search for 1401 on youtube.

Keep in mind that my  older videos showcase older versions of the simulator, with worse graphics and furnishing.
For the features shown in newer videos you may make sure that you use the latest version.

the simulation: downloads & documentation

download page     (v. 0.2.15   2021-10-15)     changelog

pinboard             (useful tables)
did you know...   (fun facts)

discord      discussion forum

facebook          (not that frequently updated; just for presence)
instagram         (not that frequently updated; just for presence)

see for a quick download, installation and use walkthrough video for the simulator.


recommended text books for the start: (local copies from and, see -alt-)

start with this one:


more easy, a bit more generalized, for self-study

A_Guide_to_1401_Programming_1961.pdf -alt- pragmatic, detailed, self-study, reprint of original IBM personal study program "Principles Of Programming"
A24-3144-2_1401_operGuide.pdf -alt- original IBM documentation, handling the system
A24-1403-5_1401_Reference_Apr62.pdf -alt- original IBM documentation, contains all CPU instructions with detailed description



SPS (Symbolic Programming System) programming

additional information resources for the 1401 and general classic computing

Computer History Museum CA  1401 lab    (the west coast 1401)
Living Computers Museum + Labs
The National Museum of Computing UK
The Computer Sheds UK
TechWorks!  2021 system startup              (the east coast 1401)

references / credits / copyrights / trademarks:

This project is based on the work of the IBM 1401 team at the Computer History Museum,
the videos and information of CuriousMarc, and the documents made available via

The 1401 simulator is intended solely for educational and informational purposes.
We do not guarantee any usefulness or correctness.
It may be distributed and used freely as a whole; add credits and link to this page.
Use in commercial settings allowed (e.g. training / education), but commercial distribution prohibited (e.g. SW collections).
This SW is not public domain. Any disassembly or extractrion of its parts or assets or algorithms is not allowed.
Any third party rights still apply and remain unaffected.

This program is an enthusiast's project and is not related to or promoted by IBM
All assumptions are based on manuals and other people's videos and websites, so take it with a grain of salt.
If you encounter poblems or have suggestions for improvement, feel free to contact me via email or have a look at the discord server.

There's no kind of user data collection implemented directly into the 1401 simulation,
nevertheless we can't speak for the used framework (Unreal Engine and the PlugIns).
Please turn to Epic Games' website if you wish for further information.
However no network connection needed; you may block any traffic e.g. in the OS firewall.

IBM® is a trademark of the International Business Machines Corporation link

The 1401 simulator uses Unreal® Engine. Unreal® is a trademark or registered trademark of Epic Games, Inc. in the United States of America and elsewhere.
Unreal® Engine, Copyright 1998 – 2021, Epic Games, Inc. All rights reserved. Unreal Engine is a product of the Epic Games Inc. link

contact: Michael Schuetz,  contact , or the discord
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