Dragon DOS is as reliable as any other 5" disk system - but disks do get corrupted, especially if you are prone to spilling coffee all over them! So you have your treasured program on a disk which has just fallen in the milk shake, and you've forgotten to make a back up of the disk. Trying to run the program just gets you an ?RF error - what do you do? Answer, get the Doctor - well the Disk Doctor anyway!

The first real Disk Doctor program I have seen for DragonDOS is from Domino Computing. This is supplied on two double sided disks which can be inserted either way up, giving you a total of four copies of the program. The double-sided disks are really just single-sided disks with the write protect notch end index hole punched out so that the unguaranteed side of the disk can be read.

The purpose of all this is because the Disk Doctor disk cannot be copied because some of the sectors have been formatted in a format unknown to DragonDOS, so the Backup command fails, Unfortunately, there are so many sticky labels all over the disk that it frequently got stuck in my drive and had to be prised out!

The software is a mixture of protected Basic and machine code routines. As well as the Disk Doctor itself, there are a number of utilities offered. For example, all the 'killed files' can be restored providing no new informtion has been put on the disk since the files were erased. The files appear as NAME101, NAME102 and so on in the directory.

Another option allows you to view the files which are flagged as being erased from the disk, but are still in the directory. Output can be sent to the screen or printer. All the files on a disk can have the protection bit set or cleared in one go using the Protection option.

One of the least useful utilities is to send a directory listing to the printer, that is a DIR to printer rather than screen. What's wrong with POKE 111,254:DIR, I want to know? A much more useful utility gives full information on all entries on the directory track. The name, type, start end and execute addresses are displayed, together with the track and sector numbers used by the file.

DragonDOS owners have probably found for themselves that you can save a program to disk with no name as in SAVE" ", but you cannot kill it off, or rename it. Another of the utilities on this disk will rename all null-named files to DOMINO1, DOMINO2 etc, so that you can rename them or kill them off.

The final utility will verify all tracks and sectors of a disk, reporting faulty ones. It does this simply by using the SREAD command and trapping disk errors.

Some of these utilities will probably be of use to most users from time to time, although most could easily be written yourself given the DragonDOS Programmer's Guidebook. However, what makes this disk worthwhile is the Disk Doctor program.

This is fully automated, and works basically as follows. The program attempts to read through the corrupted disk, noting which sectors cannot be read. It then checks through the directory and finds which files use the corrupted sectors. These sectors are replaced with clean ones containing REM statements on the 'repaired' disk.

The program is not 100% successful at restoring damaged disks, but performed very well on my few corrupted disks. Disk Doctor and its Utilities will work with either a single or double drive system. You are asked how many drives you have at the beginning of the program. Interestingly, the program will not perform operations on itself!

If not for a couple of minus points I would suggest that Disk Doctor is a valuable must for all DragonDOS owners. However, the price is not realistic at £19.45. The double-sided method makes a mess of the disks the program is supplied on, and the manual is not up to much at all. However, the manual I saw was only a draft version, so perhaps it will be transformed into something decent for the production copy.

Disk Doctor is a very useful and well written program which will be genuinely useful to users. If you can justify the cost then I recommend it. A Delta Dos version of the program should be available shortly.