Usually DOS format supports 8.3 file format.
You may see the folder name c:\program files on each windows operating system.
If you are using MS-DOS prompt (under 16 bit), the folder names will be truncated into 8 characters - that is progra~1.
In case, if you have two folders like given below:
then MS-DOS format would be the following:
The same logic goes for filenames also. This restriction in only if you are working with 16 bit applications.