With GET  EDIT,  reads  a  'w'-character  string  composed  of  the
  characters  0, 1, 2, 3, 4, 5, 6, 7 and converts it to a bit string;
  with PUT EDIT, converts 'w' 3-bit fields within  the  corresponding
  value to a string of the characters 0, 1, 2, 3, 4, 5, 6, or 7.

  B3 [ (w) ]

  w:

  A nonnegative integer or an expression capable of  being  converted
  to  an  integer that specifies the width in characters of the field
  in the stream.