Difference between revisions of "UNSIGNED"

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'''_UNSIGNED''' defines a numerical value as being positive using '''QB64''' only.
{{DISPLAYTITLE:_UNSIGNED}}
[[_UNSIGNED]] defines a numerical value as being only positive.




:::::''Syntax:'' [[_DEFINE]] LetterRange AS [_UNSIGNED] datatype
{{PageSyntax}}
: [[DIM]] {{Parameter|variable}} [[AS]] [{{KW|_UNSIGNED}}] {{Parameter|datatype}}


: [[_DEFINE]] {{Parameter|letterRange}} [[AS]] [{{KW|_UNSIGNED}}] {{Parameter|datatype}}


* 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~&


{{PageDescription}}
* Datatype can be any of the following: [[INTEGER]], [[LONG]], [[_BIT]], [[_BYTE]], [[_INTEGER64]], [[_OFFSET]]
*'''[[SINGLE]], [[DOUBLE]] and [[_FLOAT]] variable types cannot be _UNSIGNED.'''
* [[_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 (~)''', right before the number's own type suffix: {{Parameter|variableName~&}}


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


::::00000001 - unsigned & signed are both 1
<center>How negative values affect the [[_UNSIGNED]] value returned by a [[_BYTE]] (8 bits). </center>
::::01111111 - unsigned & signed are both 127
{{WhiteStart}}
::::11111111 - unsigned is 255 but signed is -1
                        00000001 - unsigned & signed are both 1    
::::11111110 - unsigned is 254 but signed is -2
                        01111111 - unsigned & signed are both 127  
::::11111101 - unsigned is 253 but signed is -3
                        11111111 - unsigned is 255 but signed is -1
                        11111110 - unsigned is 254 but signed is -2
                        11111101 - unsigned is 253 but signed is -3
{{WhiteEnd}}


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


:DIM n AS _UNSIGNED INTEGER
{{PageExamples}}
:DIM pn AS _UNSIGNED INTEGER
''Example 1:''  In '''QB64''', when a signed [[INTEGER]] value exceeds 32767, the value may become a negative value:
:LOCATE 3, 6: PRINT "Press Esc to exit loop"
{{CodeStart}} '' ''
:FOR n = 1 TO 80000
i% = 38000
::_LIMIT 10000 ' 6.5 second loops
{{Cl|PRINT}} i% '' ''
::LOCATE 12, 37: PRINT n ' display current value
{{CodeEnd}}{{OutputStart}}-27536
::IF n > 0 THEN pn = n 'find highest value
{{OutputEnd}}
::IF n = 0 THEN Count = Count + 1: LOCATE 14, 37: PRINT "Count:"; Count; "Max:"; pn
:''Explanation:'' Use an [[_UNSIGNED]] [[INTEGER]] or a ~% variable type suffix for only positive integer values up to 65535.
::IF INP(&H60) = 1 THEN EXIT FOR ' escape key exit
:NEXT n
:END




''Explanation:'' The maximum value can only be 65535(32767 + 32768) so the FOR loop repeats itself. Remove the _UNSIGNED parts and run it again.
''Example 2:'' In '''QB64''', [[_UNSIGNED]] [[INTEGER]] values greater than 65535 cycle over again from zero:
{{CodeStart}} '' ''
i~% = 70000
{{Cl|PRINT}} i~% '' ''
{{CodeEnd}}{{OutputStart}} 4464
{{OutputEnd}}
:''Explanation:'' In QB64 an unsigned integer value of 65536 would be 0 with values increasing by the value minus 65536.  




''Example 3:'' Demonstrating how _UNSIGNED variables expand the [[INTEGER]] range.
{{CodeStart}} '' ''
{{Cl|DIM}} n {{Cl|AS}} {{Cl|_UNSIGNED}} {{Cl|INTEGER}}
{{Cl|DIM}} pn {{Cl|AS}} {{Cl|_UNSIGNED}} {{Cl|INTEGER}}
{{Cl|LOCATE}} 3, 6: {{Cl|PRINT}} "Press Esc to exit loop"
{{Cl|FOR...NEXT|FOR}} n = 1 {{Cl|TO}} 80000
  {{Cl|_LIMIT}} 10000 ' 6.5 second loop
  {{Cl|LOCATE}} 12, 37: {{Cl|PRINT}} n ' display current value
  {{Cl|IF...THEN|IF}} n > 0 {{Cl|THEN}} pn = n ' find highest value
  {{Cl|IF...THEN|IF}} n = 0 {{Cl|THEN}} Count = Count + 1: {{Cl|LOCATE}} 14, 37: {{Cl|PRINT}} "Count:"; Count; "Max:"; pn
  {{Cl|IF...THEN|IF}} {{Cl|INP}}(&H60) = 1 {{Cl|THEN}} {{Cl|EXIT|EXIT FOR}} ' escape key exit
{{Cl|NEXT}} n
{{Cl|END}} '' ''
{{CodeEnd}}
{{OutputStart}}


''See also:'' [[DECLARE]], [[SUB]], [[FUNCTION]], [[DIM]], [[_DEFINE]], [[DEFSTR]], [[DEFLNG]], [[DEFINT]], [[DEFSNG]], [[DEFDBL]], [[ABS]], [[SGN]]
  Press Esc to exit loop






==Navigation:==


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                          Count: 13 Max: 65535
 
 
{{OutputEnd}}
''Explanation:'' The maximum value can only be 65535 (32767 + 32768) so the FOR loop repeats itself. Remove the [[_UNSIGNED]] parts and run it again.
 
 
 
{{PageSeeAlso}}
* DECLARE, [[SUB]], [[FUNCTION]]
* [[DIM]], [[_DEFINE]]
* [[DEFSTR]], [[DEFLNG]], [[DEFINT]], [[DEFSNG]], [[DEFDBL]]
* [[INTEGER]], [[LONG]], [[_INTEGER64]]
* [[ABS]], [[SGN]]
* [[Variable Types]]
 
 
{{PageNavigation}}

Latest revision as of 01:56, 20 April 2020

_UNSIGNED defines a numerical value as being only positive.


Syntax

DIM variable AS [_UNSIGNED] datatype
_DEFINE letterRange AS [_UNSIGNED] datatype


Description

  • Datatype can be any of the following: INTEGER, LONG, _BIT, _BYTE, _INTEGER64, _OFFSET
  • SINGLE, DOUBLE and _FLOAT variable types cannot be _UNSIGNED.
  • _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 (~), right before the number's own type suffix: variableName~&


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


Examples

Example 1: In QB64, when a signed INTEGER value exceeds 32767, the value may become a negative value:

i% = 38000 PRINT i%

-27536

Explanation: Use an _UNSIGNED INTEGER or a ~% variable type suffix for only positive integer values up to 65535.


Example 2: In QB64, _UNSIGNED INTEGER values greater than 65535 cycle over again from zero:

i~% = 70000 PRINT i~%

4464

Explanation: In QB64 an unsigned integer value of 65536 would be 0 with values increasing by the value minus 65536.


Example 3: 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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