PROC hello.world (CHAN BYTE keyboard?, screen!, error!)
  --{{{
  SEQ
    screen ! 'H'
    screen ! 'e'
    screen ! 'l'
    screen ! 'l'
    screen ! 'o'
    screen ! ' '
    screen ! 'W'
    screen ! 'o'
    screen ! 'r'
    screen ! 'l'
    screen ! 'd'
    screen ! '*c'
    screen ! '*n'
  --}}}
:
