How to install MS DOS 1.25 on 86Box?

April 11, 2022

In the last few tutorials we were roaming the lands of CP/M. But now we are entering the vast empire of Microsoft and IBM. Let's start with MS DOS 1.25 on 86Box. DOS 1.x was very limited in what it could do. It could start applications (.COM and .EXE), and process batch files (.BAT). MS DOS 1.25 worked with 320KB floppies and did not support folders (all files had to be in the root). The command interpreter supported the following commands:

DIR, TYPE, COPY, ERASE, RENAME
PAUSE, REM

No pipes, redirection, or device drivers were supported. The DOS API in 1.0 was very limited. MS-DOS 1.25, the equivalent of PC-DOS 1.10, was the first version licensed to OEMs beyond IBM or Seattle Computer Products. Some vendors labelled their versions of MS-DOS with different names and version numbers.

You need to download the following file to follow this tutorial:

MS DOS 1.25 CDP OEM archive

MS DOS 1.25 was not sold as a retailed package. It was only available to OEMs. In this tutorial we use the Columbia Data Products OEM that works well on IBM PC clones.

Creating the Virtual Machine

If you have not installed 86Box yet, see our tutorial on how to do so on windows and on Linux.

Open the 86Box Manager. Click on Add and enter the details for your VM. Tick the "Configure this VM now" checkbox. Then click on Add.

Leave the Machine type to 8088. In the Machine Dropbox, choose [8088] OpenXT. Change the speed to 16 and memory to 640 KB. Click on OK.

Now extract the MS DOS 1.25 archive and open the extracted folder. Go to the images folder inside it and copy the file called CDPDOS.IMG to the VM folder.

Now back on the 86Box Manager, click on Start. The VM will start. Click on Media > Floppy 1 > Existing Image and choose the CDPDOS.IMG file.

Press any key to start MS DOS 1.25. When asked for Date and time, just press enter. Do not enter anything. MS DOS 1.25 has problems with dates later than year 2000, so it is best to leave the default date set.

You can enter the DIR command to see the list of files:

That's it. We used MS DOS 1.25. You can now close the VM window. The next time you start it, you do not need to insert the disk file again. MS DOS 1.25 will start without any problem. Read the manual linked below to learn more about MS DOS 1.25. Also read the manuals which I posted with the IBM PC DOS 1.10 tutorial because they are more detailed and MS DOS and PC DOS are almost same at this stage.