Q32730: Use Logical AND to Determine Which Bits Are Set in an Integer

Article: Q32730
Product(s): Microsoft Visual Basic for Windows
Version(s): 1.0,3.20,3.20 and later,4.0,4.0b,4.5,7.0,7.1
Operating System(s): 
Keyword(s): 
Last Modified: 13-SEP-2001

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The information in this article applies to:

- Microsoft Visual Basic for MS-DOS 1.0 
- Microsoft QuickBASIC for MS-DOS, versions 4.0, 4.0b, 4.5 
- Microsoft BASIC Compiler for MS-DOS and OS/2 
- Microsoft Basic Professional Development System (PDS) for MS-DOS and MS OS/2, versions 7.0, 7.1 
- Microsoft QuickBASIC Compiler for the Apple Macintosh, version 1.0 
- Microsoft GW-Basic Interpreter, versions 3.20, 3.20 and later 
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SUMMARY
=======

The logical AND operator can be used in Basic to determine which bits are set.
For example, the program below determines whether a bit has been set in the High
or Low byte of a 2-byte integer variable.

MORE INFORMATION
================

The CALL INTERRUPT or INT86OLD functions in Visual Basic for MS-DOS return
information by setting certain bits in the AH or AL register. The program listed
below determines whether a bit has been set in the High or Low byte of a 2-byte
integer variable:

  ' To try this example in VBDOS.EXE:
  ' 1. From the File menu, choose New Project.
  ' 2. Copy the code example to the Code window.
  ' 3. Press F5 to run the program.

  INPUT x%  'Give it an integer value.
  PRINT "Bits set in the High byte of x%."
  IF x% < 0 THEN PRINT "Bit 7 set!"
  mask% = &H4000
  FOR i% = 6 TO 0 STEP -1
     IF x% AND mask% THEN PRINT "Bit"; i%; " set!"
     mask% = mask% \ 2
  NEXT
  PRINT "Bits set in the Low byte of x%."
  ' For just the Low byte, mask% starts out as 128.
  FOR i% = 7 TO 0 STEP -1
     IF x% AND mask% THEN PRINT "Bit"; i%; " set!"
     mask% = mask% \ 2
  NEXT

Additional query words: VBmsdos QuickBas BasicCom 1.00 2.10 3.11 3.20 3.22 3.23 4.00 4.00b 4.50 6.00 6.00b 7.00 7.10

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Keywords          :  
Technology        : kbHWMAC kbOSMAC kbVBSearch kbAudDeveloper kbZNotKeyword2 kbBASICSearch kbQBASIC100Mac kbQBASICSearch kbGWBASICSearch kbGWBASICInt320 kbZNotKeyword3 kbBASICPDS700DOS kbBASICPDS710DOS kbBASICPDS700OS2 kbBASICPDS710OS2 kbGWBASICIntSearch kbQBASIC400 kbQBASIC400b kbQBASIC450 kbVB100DOS
Version           : :1.0,3.20,3.20 and later,4.0,4.0b,4.5,7.0,7.1

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