After mentioning DOS in Programming in Pascal I Downloaded FreeDOS 1.3. I had previously installed VirtualBox on Ubuntu 22.04 system using Synaptic Package Manager. For the installation I followed How to install FreeDOS on VirtualBox. It seems that I have a later version of VirtualBox than the video, so I did not see exactly what is in the video, but it was close enough. Per the video I used the VDI file type for the VM file. The installation was successful. A couple notes:

1. When loading the live CD per the video I got a message about being unable to load all packages. Need to add more RAM(!). I had the 32MB specified. So I ignored the message and was able to start setup anyway to create my C drive. I think the LiveCD was trying to create a RAMDisk, another DOS concept that you never hear about on modern systems.
2. I have two monitors on the host machine. I used one to watch the video, and the other to actually do the installation steps. This did not work quite as well as I had hoped. I sometimes lost my mouse cursor while moving in and out of the VM screen. There are some subtleties about using a mouse with Virtual Box that I need to learn. Unlike the video, I did a full install. This slowed down the process, but did not cause any trouble.
3. At one point I lost the menu bar on the VM window, so I looked up VirtualBox top menu missing (not showing)? How to get it back. That menu bar has some nice features. View/Virtual Screen 1/Scale to 200% gets the window to a reasonable size for an old time monitor.