I can currently load and run MBASIC on top of FLEX, but the LOAD and SAVE commands do not work.

For some reason, LOAD does not simply open the file and read it sequentially.

I have not tried the FILES command yet, but off hand, do not think it will work either.

Did I misunderstand your earlier post that you could run MBasic under one of the simulators that works on a 6502? That is all I need. I don't need LOAD and SAVE to work in MBasic. I can program LOAD and SAVE into the simulator instead to work under Prodos, then just call the MBasic routine that runs the Basic program that gets loaded to memory.

I did this to Integer Basic as well. Use Prodos to load the IB program, then adjust some pointers to fool IB into believing it loaded a program into memory, itself. Then all I had to do was call the RUN subroutine.