The  CDOS*.*  files on this disks were developed by the  author 
whilst  changing  from CP/M to CDOS.  Having used  them  widely 
under CP/M their feature were sorely missed under CDOS.
Some  programs,  such as UCAT and FMAP appeared to need  little 
modification  and were easily changed,  SAP and COPY have  been 
almost re-written.

CDOSSAP  uses  the 'SYS.DIR' FCB create call of  CDOS  2.17  or 
higher  to  access  the  directory regardless of  its  size  or 
position on the disk.  (I think the call is in v1.07 as  well). 
Although  the  FCB  created with this call is  write  protected 
CDOSSAP  resets  that attribute bit and can then write  to  the 
directory as well as read it.

CDOSCOPY  operates  as a literal copy utility.  The  disks  are 
first  logged in and then the program flow (and constants)  are 
adjusted  to reflect the number of logical blocks on  the  disk 
(its storage capability). With S/D S/S disks it operates on all 
tracks,  but  with all others does not necessarily transfer the 
boot loader.
It  has  not been tested with 5" disks and the code  will  need 
minor mods to effect their copy. These mods should take 5 or 10 
minutes.

          GENERAL NOTES ON CDOS' UNDOCUMENTED FEATURES

When  CDOSGEN asks you whether the drive is large [L] or  small 
[S] try answering 'X'.  You will then get a menu for  Shugarts, 
etc.

The SYS.DIR open call has been discussed above. Try it.

Disk Labels.
A directory label is written to the disk by STAT and is used to 
ascertain  the  storage capacity of the disk and the number  of 
directory entries (64 to 512).
The last 8 bytes of the first boot loader sector (usually  side 
0  track 0 sector 1) are always recorded in single density  and 
contain eight bytes indicating the type of disk to the BIOS, eg
     LGSSSD
for Large (8"), Single Sided, Single Density
or   LGDSDD
for 8" Double Sided, Double Density diskettes (1.2 MBytes)

STAT  2.15  was written for a WD1797 FDC chip (it  records  the 
side  numbers  into the address fields) although a  WD1793  was 
eventually used.  CDOS 2.36 does not support the 1797, however, 
and this chip will not work instead of the 1793 on the 16FDC.

Double Density Recording Format:
16 sectors of 512 bytes are used per track.(MFM)
A 12 interleave is used (1,C,7,2,D,8,3,E,9,4,F,A,5,10,B,6)
Although  a 4 interleave can be read as COM files in my 4MHz no 
wait state system a 6 interleave speeds throughput by a  factor 
of  two.  (use 1,2,3,4,5,6,C,D,E,F,10,7,8,9,A,B).  INIT can  be 
modified  to  do  this..  if  interested write me  and  I  will 
disclose all....

Finally,  if  someone has deciphered how to call the 2.36  BIOS 
directly without getting error returns I am all ears...

Trevor Marshall,
26 Mirrelia Way, Ferndale, Western Australia 6155
phone International (619)4576049   or national (09)457 6059
14 December 1980

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