Mounting Disk Images

In order to use a disk image located on an SD card or the DriveWire server, SDC-DOS requires that the image be mounted into one of the four drives recognized by Disk Basic.  Images contained on an SD card can only be mounted in the first two drive positions (drive 0 and drive 1).  DriveWire images can be mounted into any drive position.  The Disk Basic DRIVE command has been extended to accept additional arguments for this purpose.

To mount an image on the SD card you provide the drive number (0 or 1) as the first argument followed by a string argument which specifies the path name of the requested image file:

  DRIVE n, "path name"
The firmware in the CoCo SDC does not currently support long file names.  You must ensure that the names of all files and directories which are to be accessible by the CoCo conform to the older 8.3 naming conventions.
If an image file is located in the Current Directory of the SD card, then only the file's name need be given. For files that are contained in a different directory you must provide the path to the file by including the names of each intervening directory in the path, separated by a forward slash (/). The path is interpreted as an absoulte path if the first character is a slash, otherwise it is interpreted as being relative to the Current Directory. For example, the following command could be entered to mount an image file named CHECKERS.DSK which is found in a sub-directory (of the current directory) named GAMES:


Wildcard characters (* and ?) can be used in the file portion of the path but not in the directory portion(s). Assuming there were no other files in the GAMES directory whose name started with the letters CH, the above command could be shortened to:


You may also omit the extension from the file name. In this case the system will first try to mount a file with the given name that has no extension. If no such file exists then .* is substituted for the missing extension and the system uses the first wildcard match, if any. This means the above command could be further shortened to:


Creating New Disk Images

You can create a new, blank disk image file on the SD card by adding the word NEW as a final parameter to the DRIVE command. If the specified file already exists it will not be erased or replaced.


To create a disk image in the SDF format use the NEW+ option.


A new SDF disk image is like an un-formatted floppy disk. You will need to use the DSKINI command to format the SDF image otherwise all disk operations will result in IO errors.

Using DriveWire Images

To access disk images on the DriveWire server, you use the DRIVE command as explained above but instead of a string argument identifying an image file on the SD card, you provide a DriveWire virtual drive number (prefixed with #) in the range of 0 to 63:

   DRIVE 2,#0

If you have a virtual 'hard disk' image containing an array of up to 256 floppy images, you can specify the index of the desired floppy image as a third argument to the DRIVE command:
   DRIVE 2,#0,125

Ejecting a Disk Image

In most cases it is not necessary to eject disk images under SDC-DOS. To switch disks you can simply mount a new image in place of an existing one. One situation where the need to eject does arise is when you want to move an image to a different drive number. For example, if you try to mount an image in drive 1 that is already mounted in drive 0, the system will produce an ?AO ERROR (already open). To accomplish this you must first eject the image from drive 0 by using the UNLOAD argument in the DRIVE command:

Displaying the Current Drive Configuration

To see how each of the four logical drives in Disk Basic are currently configured, enter the DRIVE command without any arguments:

This will display a drive mappings table like the one shown below:

   0: ON   GAMEPAK1.DSK  0
   1: OFF    ----        0
   2: ON     DW #0       2
   3: ON     DW #0       3

Each line in the table shows the current mapping information for one of the four logical drive numbers. The information provided in the table consists of the following.

  • The second column in the table indicates whether or not Disk Image mode is currently on or off. When Disk Image mode is off, the corresponding real floppy drive will be used instead (assuming a floppy controller is present).
  • The third column identifies the current Disk Image being mapped to the drive number.  For an image located on an SD card this will be the name of the image file.  For a DriveWire image this will be "DW #n" where n is a DriveWire server virtual drive number.
  • The fourth column shows the index of the current virtual floppy disk within the larger 'hard disk' image file (0 - 255).