Exhibition IBM 1401 emulator simulation

rolffson's 1401 datacenter 3D simulation

last updates: web site 2021-01-09, program v0.1.9  2020-11-25, minor web site corrections 2021-03-28


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

Get your own 1401 feeling at home! Download see below.

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!

This is a spare time project of a single developer, so more features and videos will come. please re-check now and then.
Currently, it's still sort of a prototype, and some details may still be missing.

BUG ALERT: currently (0.1.9) after handling cards, it's no longer possible to handle tapes, so do that first. (thx macieksoft for hint)


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

YouTube channel "the 1401 guy"
IBM 1401 - let's program, #8: calculating prime numbers (feat. a video from Ken Shirriff)    (new 2020-11-29)
IBM 1401 - let's program, #7: testing a program from the CHM 1401 team    (new 2020-11-08)
IBM 1401 - let's program, #6: reading the IBM 729 tape drive
IBM 1401 - let's program, #5b: last card was missing
IBM 1401 - let's program, #5: loading a bigger program + card data batch processing
IBM 1401 - let's program, #4: load a program from card (printing "Hello World")
(part 1..3 aren't that impressive... I was still practicing ;-) )

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

the simulation: downloads & documentation

downloads & documentation

download                         (v. 0.1.9 now with graphics settings!)

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


recommended text books: (local copy from, see -alt-)

A_Guide_to_1401_Programming_1961.pdf -alt- pragmatic, detailed, self-study, reprint of original IBM personal study program "Principles Of Programming"
Programming_the_1401_1962.pdf -alt- more easy, a bit more generalized, for self-study
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 CPU instruction information

additional information resources for the 1401 and general classic computing

Living Computers Museum + Labs
Computer History Museum CA
The National Museum of Computing
The Computer Sheds UK

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 without realization of profits
Any third party rights still apply and remain unaffected.

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 – 2020, Epic Games, Inc. All rights reserved. Unreal Engine is a product of the Epic Games Inc. link

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