Section 13,37: IMPLICIT

 Overrides implied (default) data typing of symbolic names.
 Statement format:

    IMPLICIT typ (a[,a]...)[,typ (a[,a]...)]...

    typ  Is any data type except CHARACTER*(*).  When "typ" 
         is equal to CHARACTER*len, "len" specifies the length 
         for character data type.  The "len" is an unsigned 
         integer constant or an integer constant expression 
         enclosed in parentheses, and must be in the range of 
         1 to 2**31-1.

    a    Is an alphabetical character.  If you specify a 
         range of alphabetic characters (two characters 
         joined by a hyphen), the first character must be 
         less than the second.

 The IMPLICIT statement assigns the specified data type to all
 symbolic names that have no explicit data type and begins with the
 specified letter or range of letters.  It has no effect on the
 default types of intrinsic procedures.