The relevant location will depend on the version of NAS-DOS
which you are using:
Those of you with EPROM blowers can change the relevant location
to suit your drives if necessary. Do remember” the usual
precautions and keep the original chip in case of accidents
During the modification process.
6. DISC FILES
As well as allowing programs to be stored on disc NAS-DOS allows
data to be staredand loaded. Routines are provided within NAS-DOS
itself to aueist in data storage and retrieval, and these
can be accensed directly from assembly language and Nascom ROM
BASIC. “ROM BASIC was developed long before discs were available
fon the Nascom system, and therefore the language 1tsel does not
provide any disc Commands. Access to the disc 15 therefore
achieved by patching rn the various NAS-DOS routines. This is,
Gone by means of the USR) function in BASIC, the argument
being the number of the NAS-DOS routine to be called. It is. of
course necessary to DOKE 4100,-10234 ta point the USR routine to
an appropriate translator in’ NAS-DOS itself. This slightly
auknard technique is necessary to allow the commands to be added
toa ROM BASIC itis nat. ‘a limitation of NAS-DUS. More
recently implemented languages (eg Extended BASIC) and
applications programs (eg NAS-CALC) include within them
meaningful commands for direct access to the discs via NAS-DOS.
The DIR (directory) command is an example of this facility.
Before any disc commands are used in a BASIC program under NAS-DOS
must be executed by the program to set up a link to the NAS-bOS
Commands. You must then initialise the NAS-DOS commands and
data area with an instruction of the form
When Using subsequent disc commands remember that the nuaber of
the disc drive is stored in location %560 (decimal). wo if you
want to change the dist drive accessed you aust include in the
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