UNSIGNED

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Revision as of 01:29, 27 February 2010 by imported>Cyperium
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_UNSIGNED defines a numerical value as being positive using QB64 only.


Syntax

_DEFINE LetterRange AS [_UNSIGNED] datatype


Description

  • Although _UNSIGNED values can use negative values the result subtracts from the highest value of the number's type keeping it positive.
  • Datatype can be any of the following: INTEGER, SINGLE, DOUBLE, LONG, STRING, _BIT, _BYTE, _INTEGER64, _FLOAT
  • _UNSIGNED can be used in a _DEFINE statement to set undefined variable name first letters as all positive only values.
  • Can also be used in DIM statements or Subprocedure parameter definitions following AS.
  • _UNSIGNED allows larger positive numerical variable value limits than signed ones.
  • The Unsigned variable type suffix used is the tilde ~ before the number's own type suffix: variablename~&


Examples

Example 1: How negative values affect the _UNSIGNED value returned by a _BYTE(8 bits).

00000001 - unsigned & signed are both 1
01111111 - unsigned & signed are both 127
11111111 - unsigned is 255 but signed is -1
11111110 - unsigned is 254 but signed is -2
11111101 - unsigned is 253 but signed is -3

Example 2: Demonstrating how _UNSIGNED variables expand the Integer range.

DIM n AS _UNSIGNED INTEGER DIM pn AS _UNSIGNED INTEGER LOCATE 3, 6: PRINT "Press Esc to exit loop" FOR n = 1 TO 80000 _LIMIT 10000 ' 6.5 second loop LOCATE 12, 37: PRINT n ' display current value IF n > 0 THEN pn = n ' find highest value IF n = 0 THEN Count = Count + 1: LOCATE 14, 37: PRINT "Count:"; Count; "Max:"; pn IF INP(&H60) = 1 THEN EXIT FOR ' escape key exit NEXT n END

Press Esc to exit loop 65462 Count: 13 Max: 65535

Explanation: The maximum value can only be 65535(32767 + 32768) so the FOR loop repeats itself. Remove the _UNSIGNED parts and run it again.


See also




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