48K Disk Basic is a system for Sinclair +3 machines which gives
compatibility with 48K programs (such as BIAS) together with a flexible
disk interface which includes an extended CAT command and a COPY command
which can copy disk files to and from tape.

Included in the zip file is a text file giving full details of the features
offered by 48KDB.  Also included are the boot program and machine code and a
disk relabelling program for the extended catalogue, all in xzx save-file
format.  That format is as follows:

  bytes 0-3:  the characters "ZXF1"
  bytes 4-20: a Spectrum tape header
  bytes 21-:  the file's contents.

The data from each file can therefore be extracted by stripping off the
first 21 bytes.

Note: This software is only suitable for version 4.0 machines.  The version
number is contained in the system test message, which may be obtained by
going to the TV test screen (hold the break key and press reset) and then
pressing together the keys Q, A, Z, P, L and M.