Q. How to define a Filename in DOS?

Each file is given a name so that it can be referred to later. This name is termed as Filename. The filename in DOS can be up to eight alpha-numeric characters long. Optionally it can also have a period (.) followed by an extension name. The extension name should be up to three characters long. For example, consider the following filename:

                 REPORT2

                 PROGRESS.DOC

REPORT2 is a filename. This filename does not have an extension name - 'DOC'. Its optional to use of an extension name in a filename . However, the extension name help out in organizing and identifying a file. For example 'DOC' may suggest that it is a document file and 'COM' may suggest that is a command file. If you use an extension name with a filename, usually you will have to identify the complete file name, normally you will have to specify the complete file name (i.e. contain the extension name) when using it with DOS commands. While giving names to files, you can use the following characters in filename:

 #, $,@, %, ^, &, -, _,',{},( ),~,0-9,a-z,A-Z

You cannot use other characters, such as semicolon (;), colon (:), coma (,), <, >, \, /, etc. in filename. Moreover, you should not use space in filenames. Some examples of invalid file names are:

Filename                                            Reason

SALE 2                                               Contains space

PROGRESSER                                     Contains more that eight characters

MY, File                                              Contains commas

CHAP_01.DOC4                                 Extension name contains more than 3 characters

If you use more than eight characters in the filename or more than three characters in the extension name, DOS may automatically shorten the filename by removing extra characters. Except this, some file names, such as COM 1, COM 2, LPT1, com and PRN are reserved by DOS for its own use. Therefore, do not use these names to name your file. Also, keep in mind that every DOS application programs including Excel, Word, WordStar, Base III PLUS AND Fox Pro follow the same file naming convention.