The name can be up to eight characters in length. It is a good idea to choose a name that describes the contents of the file. You can use any characters except blank spaces and the following symbols:
* \ / [ ] : < > + = ; . ?
The extension is optional and can be up to three characters long. You can use the extension to describe the type of data contained in the file-for example, TXT for a text file. When you use an extension, separate it from the filename with a period, like this:
DATA.TXT
Many application programs automatically add extensions to the data files you create. Lotus® 1-2-3® Release 2, for example, automatically uses the extension .WK1 for worksheet files. Microsoft Word@ uses .DOC for its word processing files. Such default extensions help an application program distinguish its own data files from files created by other programs. If you have programs that use default extensions, avoid using those particular extensions in other contexts.
You can type the name and the extension in either lowercase or uppercase letters, but do not use uppercase or lowercase letters to distinguish between files. After you type the filename, MS-DOS converts all lowercase letters to uppercase.
Using Directories
MS-DOS organizes files by storing them in directories. This makes it easy for you to find and manage your files. Directories also list specific information about each file, including the filename, the size of the file, and the date and time you last modified the file.
3-6 Using MS-DOS With Your Computer_ _