DOS (as a text based operating system) is no longer available from Microsoft as a product that you can purchase to place on your computer. The latest versions from Microsoft (Windows 95, 98, SE, and ME) are all bloated graphical versions of the operating system.
There is a version of DOS that is still available that will allow you to run your computer with a text based operating system that is fully compatible with all of the old DOS programs that you might still have. This operating system has gone by various names depending on which company owned the product at the time. Variously, it has gone by the names DR-DOS (when it was owned by Digital Research who originally developed it as an alternative to MS-DOS), Novell DOS, Caldera openDOS, and now back to DR-DOS (since it was purchased by DeviceLogics). This operating system is available to purchase from the Official DR-DOS website. You might also like to check out Club DR-DOS.
This article written by Stephen Chapman, Felgall Pty Ltd.