A control edit descriptor takes one of the following forms:

     c  nc  cn

     c     Is a format code (X, T, TL, TR, SP, SS, S, BN, BZ,
           P, /, '...', "...", Q, \, $, or :).

     n     Is an optional number of character positions.

  The term "n" must be a positive, unsigned, integer constant or a
  variable format expression.

  For all format codes (except P), the value of "n" must be within
  the range 1 through 2147483647 (2**31-1); actual useful ranges may
  be constrained by record sizes (RECL) and the file system.

  The P edit descriptor is an exception to the general control edit
  descriptor syntax.  It is preceded by a scale factor, rather than a
  character position specifier.  The value of "n" for P must be
  within the range -128 to 127.

  Control edit descriptors can be grouped in parentheses and preceded
  by a group repeat specification.