How to Determine the Size of a User-Defined Data Type

• Microsoft Fortran PowerStation for Windows 95 and Windows NT, version 4.0

SUMMARY

The Fortran Run-Time Library included with Microsoft Fortran PowerStation version 4.0 does not include an intrinsic function or subroutine that can return the number of bytes in use by a single user-defined data type variable. You can, however, use the LOC() intrinsic function to obtain the starting addresses of two user-defined data type variables, contiguous in memory, and subtract their addresses resulting in the number of bytes used by one variable of this type.

MORE INFORMATION

Do the following to calculate the number of bytes in use by a single user- defined data type variable:

1. Create a two-element array variable of any user-defined data type.

2. Use the LOC() intrinsic function to obtain the starting memory addresses for both user-defined data type array elements.

3. Subtract these addresses from each other. This will yield the number of bytes used in memory by this type of user-defined variable.

Sample Code to Illustrate Technique

C Compile options needed: none

      type udt
          integer a
          real b
      end type
      type (udt) myt(2)
      print *, 'Number of bytes used: ', loc(myt(2)) - loc(myt(1))
      end

Program Output

Number of bytes used: 8