Open Watcom FORTRAN 77 Language Reference

FORTRAN Statements
2.60 MAP Statement
MAP
The MAP statement is used in conjunction with the END MAP declarative statement. The MAP statement
marks the start of a memory mapping structure. A MAP structure must appear within a UNION block. Any
number of variables of any type may appear within a memory map. At least two MAP structures must
appear within a UNION block. A UNION block permits the mapping of the same storage in several
different ways.
The following example maps out a 4-byte integer on an Intel 80x86-based processor.
Example:
STRUCTURE /MAPINT/
UNION
MAP
INTEGER*4 LONG
END MAP
MAP
INTEGER*2 LO_WORD
INTEGER*2 HI_WORD
END MAP
MAP
INTEGER*1 BYTE_0
INTEGER*1 BYTE_1
INTEGER*1 BYTE_2
INTEGER*1 BYTE_3
END MAP
END UNION
END STRUCTURE
RECORD /MAPINT/ I
I%LONG = ’01020304’x
PRINT ’(2Z4)’, I%LO_WORD, I%HI_WORD
END
For more information, see the chapter entitled "Structures, Unions and Records" on page 167.
MAP Statement 107