msx .cas loading

Loader"cas:",r

without r not loading.

Why do you believe it's not loading without the ,R? I.e., what did you expect to see if it loaded correctly without ,R, and what did you actually see instead?

That's up to the program you run. If it does a RET back to BASIC after doing its work, you'll be back at the BASIC prompt (or the program that was running and loaded that file will continue running). If the program decides to take over the machine, there's not much you can do about it but hit the reset button.

If you just load the program with BLOAD "CAS:" (no ,R at the end), the program will be in memory and you can carry on. And you can call it later if you know the (or an) entrypoint address to use. (If you don't, I believe that there are some memory locations that hold the start and end load addresses and the entrypoint addresses that were read from the start of the file you BLOADed.)

If you're trying to do something in particular, it might help if you describe exactly what program you're loading and what you're wanting to do.

Msx have run but not adress After run.

Do you mean the RUN command? That's only used to run BASIC code. To execute machine-language code from BASIC you need to set the address with DEFUSR and then call the USR function you defined.

For example, if the address you wish to call is $D000, you can type:

    DEFUSR=&hD000
    A=USR(0)