%N hdprsnt %F $MIR/src/subs/headio.c
%D Determine if a header variable is present.
%P mjs
%: header-i/o
%B
FORTRAN call sequence:
        logical function hdprsnt(tno,keyword)
        integer tno
        character keyword*(*)

  Check if a particular header variable is present in a data set.

  Input:
    tno         File handle of the data set to check.
    keyword     Name of the header variable to check for.               
