Allocation new OSBYTE numbers
Make proposals here for new OSBYTE calls. Give a brief outline of what you want your call to do, and an outline of parameters. Bear in mind that calls below &80 can only pass and return a single 8-bit value in the X register, only calls above &7F can pass and return both X and Y - but there are no spare calls above &7F, other than subcalls of OSBYTE &A3.
If porting a BBC-like OS to another platform there are some OSBYTE variables (&A6-&FF) that may become available due to the different hardware.