  plsym(n, x, y, code)
  ********************

  plsym

  Marks out a set of n points at positions (x[i], y[i]), using the symbol
  defined by code. The code is interpreted as an index in the Hershey font
  tables.

  n (PLINT, input): Number of points to be marked.

  x (PLFLT *, input): Pointer to array with set of x coordinate values for
  the points.

  y (PLFLT *, input): Pointer to array with set of y coordinate values for
  the points.

  code (PLINT, input): Code number for the symbol to be plotted.

