SUBST and JOIN

In the Jan/Feb, 1996, issue of The HP Palmtop Paper we offered a Quick Tip about the DOS SUBST command. It's one of the external DOS commands that HP omitted from the Palmtop.

In short the SUBST command lets you substitute a fictitious disk drive label for a directory.

Before you use the SUBST command you must put the line LASTDRIVE=M in your CONFIG.SYS file and reset the Palmtop. Now you can use the command

SUBST C:\BC\INCLUDE H:

and press Enter. At this point the directory C:\BC\INCLUDE will become a fictitious H: drive on your computer. If you issue the above command before you start System Manager, the H: drive will show up in Filer and you can point to it to get a list of all the files in C:\BC\INCLUDE

If you want, you could use the command SUBST B: C:\BC\INCLUDE and make use of the non-existent B: drive on the Palmtop. If you use this command before starting System Manager you'll be able to open Filer and highlight the [B:] drive and press Enter. You'll see the files in C:\BC\INCLUDE rather than the error message "Drive not ready." Be forewarned however: the command to break the substitution, namely SUBST B: /D will fail. On a typical PC the B: drive is mapped to the A: drive and SUBST can't remove a B: drive. The only way to undo this operation on the Palmtop is to reset the computer.

There's another external DOS command that HP omitted from the Palmtop. It's the opposite of the SUBST command : JOIN.

The command JOIN D: C:\DDRV will create an empty DDRV directory on the C: disk of the Palmtop. and join that directory to the actual D: drive in ROM.

If you issue the JOIN command before you start System Manager, the directory DDRV will appear in Filer. When you highlight DDRV and press Enter you'll be looking at the files and directories on the D: drive.

If you have a 32 or 64 Mbytes Palmtop you could also use the command JOIN C:\FDrive F:.

(In the days of the HP Portable Plus laptop computer the JOIN command was even more useful. If you had an HP-IL card in your PC you could JOIN the hard disk of your desktop computer to a fictitious directory on the laptop and copy and move files back and forth in much the same way as you can with the HP Connectivity Pack and the Palmtop)

CAUTION: Do NOT use any of the following DOS commands on a drive that is the subject of a SUBST or JOIN command: BACKUP, CHKDSK, DISKCOMP, DISKCOPY, FDISK, FORMAT, LABEL, RECOVER, RESTORE, and SYS. Likewise do NOT use any other utility program that work with physical drives instead of logical DOS drives. This would include several of the Norton Utilities. Don't use something like DISK DOCTOR (NDD) on an SUBSTituted, or JOINed drive/directory.

You can get the SUBST.EXE and JOIN.EXE files from a complete set of MS-DOS 5.0 disks. We will also make the files available on this issue's The HP Palmtop Paper on DISK.