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Filenames

It is important to understand DOS file naming conventions and their use. Here, filenames and some special filename "tools" called wild cards and literals are described.

What is a File name?   Every program and data file is given a name to differentiate it from other programs and data files. A program is one or more computer instructions collected into a file. A data file is normally a collection of characters (or data) that make up a document, like a letter, or a database, like a collection of accounting transactions or customer records.

Descriptive filenames are normally used. For example, if you create and save a letter to Mom, you might give it the filename MOM.LTR. A letter to Dad could be called DAD.LTR. A word processing program file might have the filename WP.COM. Examine these filenames a little closer.

First, notice that each filename is meaningful. This is important if you want to know what is in a file by looking at its name. Obscure filenames are of little use when viewing a disk directory (or filename list).

Also notice that the filenames have two parts separated by a period. In our filename examples, the first part was used to differentiate Mom's letter from Dad's. The second part of the filename, called an extension, specifies the file type. These files are letters, so for convenience the extension LTR was assigned. When looking at a list of filenames, you can tell which ones are letters by looking at extensions; you can tell who the letters are to by reading the first part of the filenames.

The extension COM designates a command file type. Command files and files having the extension EXE are executable program files. You can run files having the extension COM or EXE by typing the first part of the filename. For example, in the WP.COM example, typing WP and pressing Enter causes the WP program to run. It is not necessary to type the filename extension. If you have program files having extension like OVR, WKS, DBF, HLP, or PRN, use some other extension to avoid possible confusion. \

Filenames Rules: There are a few simple rules associated with filenames. These are

1. Filenames are one to eight characters in length with an optional one-to three-character extension.

2. Filenames can include any of the following characters.
    A-Z (or a-z)
    0-9
    $ & # @ ! %' '( ) { } _ / \
    Other characters are not allowed, such as : , ; | +, as they have special meanings.

3. Reserved device names, listed and described in Table 1-4 of section 1, are not allowed.

4. A period is used to separate the first part of a filename from the extension.

5. When a filename includes an extension, include the extension when used in conjunction with a DOS command (like COPY, TYPE, or ERASE).

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