The MAGTAPE function permits your program to control unformatted  magnetic
  tape  files.   Control  of  unformatted  magnetic tape files is limited to
  rewinding, specified by 3%, 0%.

  Example

  I = MAGTAPE (3%, 0%, 2%)

1  –  SYNTAX

      int-var1 = MAGTAPE(3%, 0%, chnl-exp)