Australian PC World - Half-empty disks that tell you they're full

Half-empty disks that tell you they're full

Q I collect a lot of JPEG files from the Internet, which I store on 100MB Zip disks. While I was almost able to fill the first one I bought, two subsequent disks announced that they were full when they appeared to contain only 20MB of data.
I posted a message on a PC support site, and it was suggested that the problem lies with the FAT16 structure of Zip disks. I took this to mean that the cluster size is inefficient. I found, however, that I could release more space on the disks by creating a number of directories and grouping the files into them. Nonetheless, I still could only utilise about 30MB of the new disks.
If the problem really is with the FAT structure, this leaves two questions. Why was I able to fill the first disk, but not the subsequent ones? And why did grouping the files into folders seem to help, given that there is still the same number of files on the disks?
- Rohan Parkes

A FAT16 has been showing its age for some time. Most people know of its limitations with larger hard drives and the way it inefficiently stores files. Your problem is a little different, but FAT16 is still the cause.
FAT16 treats the root directory of any disk as a special case. There is a limit on the total number of root directory entries that can be stored in the FAT. This puts a limit on how many files can be stored in the root directory. In addition, to be able to store long filenames, Windows 95 uses multiple entries in the FAT. So the maximum number of files you can have in the root will vary. You get a message saying that the disk is full even though there is still room on the disk.
This limit does not apply to subdirectories. Normally people put relatively few files on floppy disks, or they store most files on their hard drives in subdirectories, so they never exceed the limit. With the higher capacity of Zip disks and other removable media, a lot of people try to put too many files in the root directory.
The easiest way around this is to create just a single subdirectory and put all files into that directory. Leave no or few files in the root directory. If you need to put files in the root directory, keep the filenames short.
- Roy Chambers

Category: General, Win95
Issue: Mar 1998
Pages: 150