MadSci Network: Computer Science

Re: Are empty files taking any space on the hard drive ?

Date: Fri Dec 14 16:19:50 2001
Posted By: Mike Westerfield, Staff, Computer Science, Byte Works, Inc.
Area of science: Computer Science
ID: 1004501618.Cs

The empty file does take up some space, sort of, but it may or may not
actually have any impact on the free space left on your disk.

What follows applies to the Windows 9x operating system.

Every file on disk has an entry in a special kind of file called a
directory. This is the file programs read to tell you what files are
actually on your disk. Before long file names were introduced, these
directory entries took 32 bytes each; now they can vary in length. Poking
around with the DEBUG utility, I verified that when you create your zero
length file, you don't actually use up any room on the disk for the file
contents, but you do use up some space in the directory file. If the
directory file is full, it could conceivably expand, and that would take up
some space on this disk.

Some of the older books on DOS are especially good at pointing out exactly
how the disk is put together. I used "Underground DOS 6.0," by Dan Gookin,
ISBN 0-553-37097-9 as a guide.

While this answer specifically applied to Windows 9x O/S, the same general
scheme is used for every disk format I've ever looked at. All have some
form of directory entry, and every file uses some space in the directory.
In some cases, a zero length file actually uses some space on the disk,
generally the smallest amount of space you can allocate.

Mike Westerfield

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