With GET  EDIT,  reads  a  'w'-character  string  composed  of  the
  characters  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, or F; with
  PUT EDIT, converts 'w' 4-bit fields within the corresponding  value
  to a string of the characters 0 through F.

  B4 [ (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.