This article explains what a DO file is, how to open it, and how to convert it to another format that may be easier to use in your program of choice.
A file with the extension .DO may be a Java servlet file. It is used by Java web servers to deliver web-based Java applications.
Other DO files are most likely Stata batch analysis files. These are usually called do files and are plain text files that contain a list of commands that are to be executed together in a series.
Similar to Stata files is the ModelSim macro file format that uses the same file extension. These types of files store macro-related commands used with Libero SoC.