Hollerith Data

Many "dusty-deck" Fortran applications store Hollerith ASCII data into numerical data objects. With the 1977 Fortran standard (and Fortran 90), the CHARACTER data type was provided for this purpose and its use is recommended. You can still initialize variables with the older Fortran Hollerith (nH) feature, but this is not standard practice. The following table indicates the maximum number of characters that will fit into certain data types. (In this table, boldfaced data types indicate default types subject to promotion by the f77 command-line flags -dbl, -r8, or -xtypemap= ).

Table 7-3 f77: Maximum Characters in Data Types

	Maximum Number of Standard ASCII Characters
Data Type	No -i2, -i4, -r8, -dbl	-i2	-i4	-r8	-dbl
BYTE	1	1	1	1	1
COMPLEX	8	8	8	16	16
COMPLEX*16	16	16	16	16	16
COMPLEX*32	32	32	32	32	32
DOUBLE COMPLEX	16	16	16	32	32
DOUBLE PRECISION	8	8	8	16	16
INTEGER	4	2	4	4	8
INTEGER*2	2	2	2	2	2
INTEGER*4	4	4	4	4	4
INTEGER*8	8	8	8	8	8
LOGICAL	4	2	4	4	8
LOGICAL*1	1	1	1	1	1
LOGICAL*2	2	2	2	2	2
LOGICAL*4	4	4	4	4	4
LOGICAL*8	8	8	8	8	8
REAL	4	4	4	8	8
REAL*4	4	4	4	4	4
REAL*8	8	8	8	8	8
REAL*16	16	16	16	16	16

When storing standard ASCII characters with normal Fortran:

• With -r8, unspecified size INTEGER and LOGICAL do not hold double.

• With -dbl, unspecified size INTEGER and LOGICAL do hold double.

The storage is allocated with both options, but it is unavailable in normal Fortran with -r8.

Options -i2, -r8, and -dbl are now considered obsolete; use -xtypemap instead.

Example: Initialize variables with Hollerith:

---

demo% cat FourA8.f
      double complex x(2) 
      data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/ 
      write( 6, '(4A8, "!")' ) x 
      end 

demo% f77 -silent -o FourA8 FourA8.f
demo% FourA8
abcdefghijklmnopqrstuvwxyz012345!
demo% 

---

If you pass Hollerith constants as arguments, or if you use them in expressions or comparisons, they are interpreted as character-type expressions.

If needed, you can initialize a data item of a compatible type with a Hollerith and then pass it to other routines.

Example:

---

        program respond
        integer yes, no
        integer ask
        data yes, no / 3hyes, 2hno /

        if ( ask() .eq. yes ) then
            print *, 'You may proceed!'
        else
            print *, 'Request Rejected!'
        endif
        end

        integer function ask()
        double precision solaris, response
        integer yes, no
        data yes, no / 3hyes, 2hno /
        data solaris/ 7hSOLARIS/
10      format( "What system? ", $ )
20      format( a8 )

        write( 6, 10 )
        read ( 5, 20 ) response
        ask = no
        if ( response .eq. solaris ) ask = yes
        return
        end

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