After you have written your MIXAL program, you'll probably want to test it. This can be done with the MIX virtual machine. First you will need to compile your code into MIX byte code. This can be done within Emacs with the command M-x compile (C-c c). In case of compilation errors, you can jump to the offending source code line with M-x next-error.
Once the program compiles without errors, you can debug or run
it. To invoke the debugger, use M-x mixal-debug (C-c d).
Emacs will open a
GUD buffer where you can
use the debugging commands described in See mixvm.
If you just want to execute the program, you can do so with M-x mixal-run (C-c r). This will invoke mixvm, execute the program and show its output in a separate buffer.