RAMDRIVE.SYS

Uses part of your computer's random-access memory (RAM) to 
simulate a fixed disk drive. This device driver must be loaded 
by a <DEVICE> or <DEVICEHIGH> command in your CONFIG.SYS file.

RAM drives are much faster than hard disk drives because your 
computer can read information faster from memory than from a 
hard disk. A RAM drive appears to be a normal fixed disk drive; 
you can use it just as you would any hard disk drive. The most 
important difference between a real disk drive and a RAM drive 
is that because it exists only in memory, information on a RAM 
drive is lost when you turn off or restart your computer. You 
can set up as many RAM drives as you want, up to the amount of 
memory your computer has. To do this, add one RAMDRIVE.SYS line 
to your CONFIG.SYS file for each additional RAM drive you want.

When I was in senior high school, computers in our school didn't 
have any hard disks. At that time, teachers let us start up the 
computers using floppy disks. The computers were all Hewlett 
Packard Vectra 80486/33 with 4MB RAM. Our teacher only taught us 
FOXBASE Plus for MS-DOS. So usually there is no need for so much 
extended memory. I thought it would be better to utilize the 
memory, so I started using RAM drive at that time.

At first, I was greatly astonished by that program --- 
RAMDRIVE.SYS. It created logical drives that were really like 
real ones. The speed of the drives were really fast. Starting 
QBasic from a RAM drive located in extended memory only takes 
less than half a second, much faster than starting from a floppy 
disk. Starting programs from a RAM drive located in conventional 
memory almost takes no time. Of course, usually a RAM 
drive is located in extended memory because conventional memory 
has a total capacity of only 640KB, and extended memory is 
almost not limited (can be as much as the amount the motherboard 
can take, usually >= 31MB, <= 4095MB).

Note: You cannot start RAMDRIVE.SYS from a command line. You 
must load it using DEVICE or DEVICEHIGH commands in the 
CONFIG.SYS file. Also, you should not start it when Windows is 
running, either Windows 9x or NT.

Windows 9x/Me startup disk creates a RAM drive of 2MB by 
default. There lie the tools for fixing Windows. You will see 
that in AUTOEXEC.BAT file of the startup disk, there is a 
command helping to find out the ramdrive. This is done with 
the help of FINDRAMD.EXE. You can use that command on any MS-DOS 
whose versions are higher than 5.0.

For more information, please refer to MS-DOS Help or Windows NT 
command line command help.