FIX: SELECT on Characters Greater Than ASCII 127 Fails

The information in this article applies to:

• Microsoft FORTRAN for MS-DOS, version 5.1
• Microsoft FORTRAN for OS/2, version 5.1

SYMPTOMS

Code compiled that contains a SELECT CASE block which compares a CHARACTER test expression against a case which is higher than 127 in the ASCII table may produce incorrect results.

CAUSE

When the compiler generates the code for the comparison of the CHARACTER test expression against the high ASCII constant it produces an incorrect comparison against a negative number which will always fail.

RESOLUTION

When comparing against ASCII values greater than 128, use integers for the comparison and convert the test expression from CHARACTER to INTEGER using the ICHAR intrinsic function.

STATUS

Microsoft has confirmed this to be a problem in FORTRAN version 5.1. This problem was corrected in FORTRAN PowerStation, version 1.0.

MORE INFORMATION

The following code can be used to reproduce the problem:

Sample Code #1

      CHARACTER A
      A = char(128)
      SELECT CASE (A)
        CASE (' ') ! insert ASCII 128 in the quotes using ALT+KEYPAD 128
            WRITE (*,*) 'High ASCII (128)'
        CASE DEFAULT
            WRITE (*,*) 'Failed Test'
      END SELECT
      END

Sample Code #2

      CHARACTER A
      A = char(128)
      SELECT CASE (Ichar(A))
        CASE (128)
            WRITE (*,*) 'High ASCII (128)'
        CASE DEFAULT
            WRITE (*,*) 'Failed Test'
      END SELECT
      END