- Receiving Messages (the `/MSGID=` switch):
  - By default most primitives do not forward their messages on to the macro.
  - Most macros that send messages use the `/MSGID=` switch to enable messages.
    - Using `/MSGID=MAIN` will send the messages to the macro.
    - It is common to get messages from multiple primitives and send them all to the macro.
    - Messages sent to the macro go to the `processMessage` procedure.
      (This is covered on the next page.)
  - Some of the commands that use the `/MSGID=` switch:

        PLOT     LIST     LIST2     SOURCEDG

X-Midas Users Take Note:
The `/MSGID=MAIN` in NeXtMidas corresponds to `/MSGID=1` in X-Midas. This is because NeXtMidas allows IDs to be names, not just numbers.