Allocating new OSBYTE numbers
OSBYTE calls <&80 are short OSBYTEs that only take and return a single parameter in the X register, OSBYTE calls >&7F are long OSBYTEs that take and return two 8-bit parameters or one 16-bit parameter. Unfortunately, all the long OSBYTEs are allocated, so the only remaining ones are short OSBYTEs.
However, OSBYTE &A3 is a multi-purpose OSBYTE that takes one parameter in Y for a specific application indicated by the value in X, and can return two bytes or one 16-bit value. Only a dozen or so OSBYTE &A3 calls have been allocated, so these calls could be more appropriate to use - especially if you want to be able to return 16 bits of information. High numbered OSBYTE &A3 calls should be used for something related to the similar-numbered OSBYTE call, for example OSBYTE &A3,&FD,num causes a system reset of the type specified by OSBYTE &FD.
If implementing a operating system interface on another host, then OSBYTEs can be repurposed if they perform the same function. For instance, use OSBYTE &9C (156) to control the serial port in the same manner.
Allocating new OSWORD numbers
Make proposals here for new OSWORD calls. Give a brief outline of what you want your call to do, and an outline parameter block, and also post it to StarDot.
Calls below &80 can only have up to 16 bytes control block. If your call needs more than 16 bytes it must be numbered above &7F.
Calls calls above &7F have a defined layout that specifies the size of the control block up to a maximum of 255 bytes, and a convention has grown up that byte XY+2 and XY+3 hold command and result information.
XY?0 inward control block size (required) XY?1 returned control block size (required) XY?2 command XY?3 sub-command/returned status XY!4 data XY!8 data etc.
OSWORD &B0 OSWORD &BE OSWORD &BF OSWORD &C0 OSWORD &C8 XY?0 in in in in in XY?1 out out out out out XY?2 command command command command in flags XY?3 subcommand flags result result out flags XY!4 data address URI string socket SWI XY!8 data data data R0 XY!12 etc etc length R1 etc etc etc