IBM 1401

IBM 1401 history and videos:

This is the playlist of my videos featuring the IBM 1401 at the Computer History Museum in Mountain View, California, USA

The IBM 1401, introduced in 1959 was one of the first widespread computer mainframes, with an estimated half of the world computers being IBM 1401 by the mid 1960's.

This period marketing video does a great job presenting its main features, if you can bear following the subtitles.

Even though it is enormous and hugely expensive by today's standards, it ushered a new area of "small" and "affordable" mainframes for IBM at the time.

Before the 1401, IBM mainframes were only affordable to the top government agency and the largest of businesses. The 1401 democratized the use of computers, making it affordable to medium size businesses. It it the first computer that was produced in excess of 10,000 units. By the end of the 1960's, half of the computers in the world were IBM 1401.

Key to reduce size, this is one of the first computers to use transistors instead of tubes. To further reduce costs, the CPU was small and slow compared to its large IBM brethren, and memory started at a measly 4 kB and topped out at a measly 16kB with the expensive 1406 extension. But for business use, the 1401 had it where it counted. Its peripherals were absolutely top notch, surpassing that of the large scientific mainframes. The IBM 1403 printer, at 600 line/minute, is still impressive today. The IBM 1402 card reader swallows punched cards at the impressive rate of 800 cards/minute. And it's ability to drive up to 7 of the IBM 729 magnetic tapes sealed its market appeal for business use. Tapes could hold a large amount of customer orders, inventory, payroll and other business data information. Businesses were finally able to ditch their manual ledgers and unwieldy piles of punched cards and enter the computer age.

This Computer History Museum (CHM) video is an excellent summary of the IBM 1401 history. It also shows how the CHM acquired an IBM 1401 from Germany in 2003, and then later a second machine from someone's basement in Connecticut. After several years of work, both machines have been restored to working order, and are demonstrated weekly to visitors.

Of course, it takes a lot of work to keep them working, and we keep trying and discovering new old things with them, and that's what you see in my videos.

More IBM 1401 Information

CHM article about the IBM 1401 , an introductory overview written by restoration team member Guy Fedorkow
The legendary IBM 1401 data processing system, a scientifically accurate historical paper written by team leader Robert Garner for the IEEE Journal
IBM 1401, A Modern Theory of Operation, a technical book about the inner workings of the IBM 1401, by Guy Fedorkow.
Blog articles by Ken Shirriff, a series of eye-opening, amazingly well explained, deep technical blog posts about specific 1401 topics. Ranges from cracking bitcoins on the 1401, to some deep dives into the 1406 core memory or the 1403 printer inner workings and repairs.
ibm-1401.info, our comprehensive IBM 1401 information repository maintained by team member Ed Thelen. Everything we know about the 1401 is in there, somewhere. Includes links to original documentation, discussions of specific topics by team members, original engineers interviews, etc...

Programming the IBM 1401

Everyone can write and run his own IBM 1401 programs on a PC thanks to the IBM 1401 ROPE compiler and emulator. It works on Windows, Mac and Linux. That's how we develop and test our programs too, before punching them on real cards and running them on the real 1401.

ROPE 2018-1-30.zip Note that there is a big quirk: the File->Open... menu does not work, but instead if you click on the Browse... button on the editor window, this one will work. Don't ask... The source code for the ROPE project is here: https://github.com/lucaseverini/ROPE
IBM 1401 Programs.zip . A library of example programs that you can compile and run using ROPE

Use the following references to learn how to program the very unusual IBM 1401:

http://bitsavers.org/pdf/ibm/1401/Programming_the_1401_1962.pdf: This book is a tutorial on 1401 programming. I recommend starting with this if you want to write code.
http://bitsavers.org/pdf/ibm/1401/A24-1403-1401_Reference_Apr62.pdf: Describes all of the instructions of the 1401. It includes some of the optional instructions not covered in the previous book.
http://bitsavers.org/pdf/ibm/1401/C24-3319-0_Autocoder_on_Tape_Laguage_Specifications_and_Operating_Procedures_Nov64.pdff - This reference explains Autocoder, which is the assembly compiler you'll use in ROPE to write and compile your program.
http://ibm-1401.info/1401SoftwDevel.html : an exhaustive list of software development documents

Demo Projects with the IBM 1401

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