Datcom by Holy Cows, Inc.


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Questions before you buy?  Email Bill at datcom@holycows.net

One user attempted to install Datcom+ Pro on a MacBook running a parallel desktop with Windows 7, and it did not work, so this configuration is NOT SUGGESTED.

A user has reported that it works fine under Windows 11.




To purchase a licensed copy of the Datcom+ Pro package, follow these instructions

1. Download the RequestDatcomLicense program from this link.

2. Run this program on the computer that you will be running Datcom+ Pro on. THE LICENSE CANNOT BE TRANSFERRED TO ANOTHER COMPUTER. This program collects various bits of information about your computer in order to generate a license. The file Datcom.req will be generated in a folder Datcom on your desktop. Email this file to datcom@holycows.net

3. Purchase the license through PayPal, using the same email address used when the license request file is sent. Price is $29 US. PayPal will do the conversion for you. Please note that there will be ABSOULTELY NO REFUNDS. Note: The PayPal page takes a while to load. It’s their fault, not mine. To purchase more than one license, click on the Buy Now button below, then on the PayPal site, change the quantity to the number that you want to purchase.

1 Datcom license

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4. A new license file will be generated for your computer and sent via email back to you. Generally this license file will be returned within 24 hours, 7 days a week, usually in much less time. I’m usually at my computer from 7am to 10 pm Eastern Time (United States). A link to the Datcom+ Pro package will also be sent.

5. Install the Datcom+ Pro installation package as well as the license package.



The free version is still available. It has not been updated with features of the Datcom+ Pro version. I have no way of generating a new distribution package without a LOT of work, and I’m not interested in doing that right now. It is recommended that you view the tutorial videos to see just how easy it is to use the new Datcom+ Pro. You will see how powerful this new package is, and the time saved over the free version. You will find that you are more efficient with the Datcom+ Pro package than with the free version.

Downloads here:

Windows version 2.8.5

Linux version 2.8.4

Digital Datcom User’s Manual


Once installed, to run the Datcom+ or Datcom+ Pro program, you just double-click on one of the Datcom Input Files (with .dcm extension) in the Examples directory. If you just try to run the digdat.exe program alone, it will not run correctly, and give you error messages such as “open: No such file or directory” and “apparent state: unit 5 named for005.dat”. This may also cause global warming.

B737 model warning: This model came from the NASA reports on Datcom from the 1970’s Their model is garbage. The wing airfoil is nowhere close to correct. While finding the exact airfoil is not possible, you can surely find something better than this symmetric airfoil.


There is a problem running the freeware program Datcom+ under Windows 10/11. This hack should resolve the issue. Note, this is only work if there is NOT A SPACE IN YOUR USER NAME. For example, if your username is Joe, the path should be “c:\Users\Joe\Datcom\bin”. If your username is Joe Smith and the path is “C:\Users\Joe Smith\Datcom\bin”, this hack will NOT work. There is an untested solution to that below.

If you DO NOT have a space in your username, follow these steps:

1.  Change the environment variable DATCOMROOT by clicking on the search box, and typing in “environment variables”. Click on “edit the system environment variables. Click on the Environment Variables box. Edit DATCOMROOT and remove the double quotes at the beginning and end. Click “ok” twice.

2.  In the Datcom\bin directory on your desktop, edit the Datcom.bat file. On lines 14-16, remove the double-quote (“) marks, so that the entries look like this

   set PREDAT_PROGRAM=predat

   set DATCOM_PROGRAM=digdat

   set DATCOM_MODELER_PROGRAM=datcom-modeler

3.  You should be able to run the programs now.

If you have a space in your username, you might try this. I haven’t tried it, so I don’t know if it will work. Create a new username without a space in the username, such as Datcom. Install the Datcom+ program as that user, and follow the instructions above. It should work for that new user, and potentially it will then work for your normal username with a space in it. I have not tried this, so I don’t know if it will work.


These are the PDF files of the original Datcom manual, 3070 pages of equations and methods that the Digital Datcom program is based on. Not all of the paper manual is represented in the computer program.

DATCOM complete manual from 1978 (3070 pages, 76 Meg)

Or, you can download just the sections that you are interested in, below: