File I/O and z88dk
------------------

Many machines supported by z88dk support multiple types of disc system, 
for this reason it is desirable to make it as easy as possible to switch 
between them. To this end, the file libraries for certain targets have now
been separated out from the main machine library and located in separate 
libraries. The routines which gave been isolated are:

close
creat
fdgetpos
ftell
lseek
open
open_z88
read
readbyte
remove
rename
write
writebyte

Which are all the routines required to enable file i/o. A dummy library 
called ndos.lib has been created which contains minimal stubs for these 
routines which simply return an error value.

Unfortunately, this means that if you don't require file i/o you have to 
supply an extra parameter for the compile, but I believe the flexibility 
of being able to switch between different DOS systems is worthwhile.

So far, a file library has only been prepared for one system besides the 
z88 (whose file i/o routines remain integrated) and that is for the 
Spectrum.

Spectrum:

A file i/o library has been prepared for the +3, this hasn't been tested 
but it should just work! To use it compile thusly:

zcc +zx -DPLUS3 [files] -lp3

To compile with no/dummy file io routines use:

zcc +zx [files] -lndos

In future
