echo
    WORD_134217728      # XBUF
    WORD_134217732      # XCSR
    WORD_134217736      # RBUF
    WORD_134217740      # RCSR

getchar
    LDSP+0
    LOAD
    TEST
    BRZ>getchar
    LDSP+1
    LOAD
                        # A character is now on the TOS and ready to be printed to the terminal.
putchar
    LDSP+3
    LOAD
    TEST
    BRZ>putchar
    LDSP+4
    STORE
                        # Now wait for the next incoming character.
    IM_0
    TEST
    BRZ>getchar