M20 Olivetti M20

Handling MSDOS disks on the M20 side

by Dwight K. Elvey
MSDOS disk handling with the M20

There are 2 programs written by an unknown author. These are on the PCOS 2.0f image file, available on this page. There is one pcos2dos.cmd and dos2pcos.cmd.

To use these, you need to format a disk as a 320K disk on the PC as a DOS disk. The disk is a DOS disk. The format command in DOS will let you specify the size of the disk you want to format. As an example, you may have a 720K disk drive but you may need to tell DOS what the drive size is or it might think to format a different size.

As I recall, format f:/320 will do 320K. The problem is that DOS is too smart. I've had problems with some format programs if the disk is already formatted as a 360k. In this case, DOS won't let you write over it :( By using PCOS to first format the disk, you destroy the original 360K format on the disk. Now, since DOS doesn't recognize it as a 360K disk, it will let you format it as a 320K. I've also done the same by erasing the disk with a strong magnet. It takes one of those really strong ones that if you get your finger in the way it will be quite painful. I recommend the PCOS vf command as it is a little safer :)

Of course, you need to do this on a 360K or 320K disk drive on the PC and not a 1.2M. DOS will let you do it but it is unlikely to work correctly on the M20.

The program dos2pcos will look at the directory and read the first file of the DOS disk. The program pcos2dos will write a file to the DOS disk. pcos2dos will overwrite the entire directory so any other files on the DOS disk will be destroyed. It only does one file at a time. Who ever wrote these programs didn't want to add too much to the programs.

The program pcos2dos will copy one file to the 320K DOS disk. It can later be read by the DOS system and transferred to another disk. The program dos2pcos will transfer the first file of the 320K DOS disk into PCOS file.

Both these programs only transfer a single file at a time but once one has a 320K to work with, moving files is relatively easy and faster than using a serial cable.

I've used these programs while working on setting up the hard disk and mentioned in the section on the hard disk. I mainly did this way because I was more familiar with the editor on the PC.

Although, I've not tried it, I believe the programs may also work on a 640K PCOS system. I think a couple people have those. It would be an interesting experiment. The 640K systems are more limited.

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