Shareware Grab Bag/Shareware Grab Bag.iso/013/sdir.txt

Text File | 1984-01-31 | 1.9 KB | 30 lines

              A SHORT NOTE ABOUT SDIR

     An interesting comparison can be made between the responses of
SDIR and CHKDSK when run on the same disk.  You will note that they
both agree on the amount of free space remaining on the disk.  However
if you take the trouble to add the sizes of the files as described by
SDIR you will find it adds up to less than the "amount in user files"
described by CHKDSK.  Your first response is to assume that SDIR is
wrong since it was written by a human and CHKDSK comes from IBM.
However, if you run DIR (which also comes from IBM), you will find
that it agrees -file by file- with the sizes given by SDIR.  This leads
you to conclude that CHKDSK and DIR do not agree with each other.
How come?  The answer has to do with the fact that PC-DOS -in effect-
reserves some book-keeping space to keep track of each file. The more
files you add to the disk, the more book-keeping space it reserves.
If you delete all files but one from a disk, you will find that SDIR,
CHKDSK, and DIR all agree.  In my experiments, I found that this
extra space used by the system was roughly 15% of the file size, but
I wouldn't count on this as a constant since I think it is a function
of file sizes, number of files, degree of file fragmentation,etc.
In other words, SDIR and DIR are telling you the amount of space that
the actual files are using while CHKDSK is telling you the TOTAL amount
of space that has been used up.  This also helps explain the situation
where you supposedly have 10,000 bytes left, but when you try to add
a 9,500 byte file, the system responds with "disk full".  The file
plus the added book-keeping space was actually greater than 10,000.
In other words, you can't really count on any of them other than as
an approximate guide. Terrific huh?
     Ken Eagle [phone]