The description below is from the book DOS the Easy Way by Everett Murdock Ph.D.
CLICK HERE for information about downloading the book.
Type: External (3.3 and later)
Purpose: Keeps track of the locations of files for fast access.
FASTOPEN locates files on a fixed disk by searching your disk`s directory
structure in a predetermined search pattern. After running FASTOPEN,
you use a file or directory, the program will make a record (in memory)
file`s name and location. The next time you specify that file, DOS will
first in the last known location. This reduces the time needed to access
This command is used only on fixed disks and can be used on up to four
disks at one time. For each fixed disk, you enter the number of files
to keep track of (from 10 to 999 files). If you do not enter a number,
keep track of 10 files. FASTOPEN uses about 40 bytes of memory for each
directory location it keeps track of.
You can use this command to set the number of files to track only once.
want to change the FASTOPEN settings, restart your computer.
/X - Uses expanded memory for FASTOPEN buffer space.