Difference between revisions of "UNSIGNED"

From QB64 Wiki
Jump to navigation Jump to search
imported>Clippy
m
m (Text replacement - "DECLARE" to "DECLARE")
 
(2 intermediate revisions by 2 users not shown)
Line 1: Line 1:
 
{{DISPLAYTITLE:_UNSIGNED}}
 
{{DISPLAYTITLE:_UNSIGNED}}
[[_UNSIGNED]] defines a numerical value as being positive using '''QB64''' only.
+
[[_UNSIGNED]] defines a numerical value as being only positive.
  
  
''TYPE'' {{PageSyntax}}  
+
{{PageSyntax}}  
::: [[DIM]] variable [[AS]] [{{KW|UNSIGNED}}] ''datatype''
+
: [[DIM]] {{Parameter|variable}} [[AS]] [{{KW|_UNSIGNED}}] {{Parameter|datatype}}
  
::: variable [[AS]] [{{KW|_UNSIGNED}}] ''datatype''
+
: [[_DEFINE]] {{Parameter|letterRange}} [[AS]] [{{KW|_UNSIGNED}}] {{Parameter|datatype}}
 
 
''_DEFINE'' {{PageSyntax}}
 
::: {{KW|_DEFINE}} {{Parameter|LetterRange}} {{KW|AS}} [{{KW|_UNSIGNED}}] {{Parameter|datatype}}
 
  
  
 
{{PageDescription}}
 
{{PageDescription}}
* When {{KW|_UNSIGNED}} values 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]], [[LONG]], [[_BIT]], [[_BYTE]], [[_INTEGER64]], [[_OFFSET]]
 
* Datatype can be any of the following: [[INTEGER]], [[LONG]], [[_BIT]], [[_BYTE]], [[_INTEGER64]], [[_OFFSET]]
*'''[[SINGLE]], [[DOUBLE]] and [[_FLOAT]] variable types cannot be _UNSIGNED!'''
+
*'''[[SINGLE]], [[DOUBLE]] and [[_FLOAT]] variable types cannot be _UNSIGNED.'''
* {{KW|_UNSIGNED}} can be used in a {{KW|_DEFINE}} statement to set undefined variable name first letters as all positive only values.
+
* [[_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 {{KW|DIM}} statements or Subprocedure parameter definitions following {{KW|AS}}.
+
* Can also be used in [[DIM]] statements or subprocedure parameter definitions following [[AS]].
* {{KW|_UNSIGNED}} allows larger positive numerical variable value limits than signed ones.
+
* [[_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~&
+
* The unsigned variable type suffix used is the '''tilde (~)''', right before the number's own type suffix: {{Parameter|variableName~&}}
  
  
<center>How negative values affect the {{KW|_UNSIGNED}} value returned by a {{KW|_BYTE}} (8 bits). </center>
+
<center>How negative values affect the [[_UNSIGNED]] value returned by a [[_BYTE]] (8 bits). </center>
 
{{WhiteStart}}
 
{{WhiteStart}}
 
                         00000001 - unsigned & signed are both 1    
 
                         00000001 - unsigned & signed are both 1    
Line 32: Line 28:
  
  
''Example 1:'' When a signed '''QB64''' INTEGER value exceeds 32767, the value may become a negative value:
+
{{PageExamples}}
 +
''Example 1:'' In '''QB64''', when a signed [[INTEGER]] value exceeds 32767, the value may become a negative value:
 
{{CodeStart}} '' ''
 
{{CodeStart}} '' ''
 
i% = 38000
 
i% = 38000
Line 38: Line 35:
 
{{CodeEnd}}{{OutputStart}}-27536
 
{{CodeEnd}}{{OutputStart}}-27536
 
{{OutputEnd}}
 
{{OutputEnd}}
:''Explanation:'' Use an [[_UNSIGNED]] INTEGER or a ~% variable type suffix for only positive integer values up to 65535.
+
:''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:
+
''Example 2:'' In '''QB64''', [[_UNSIGNED]] [[INTEGER]] values greater than 65535 cycle over again from zero:
 
{{CodeStart}} '' ''
 
{{CodeStart}} '' ''
 
i~% = 70000
 
i~% = 70000
Line 77: Line 74:
  
 
{{OutputEnd}}
 
{{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.
+
''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}}
 
{{PageSeeAlso}}
* [[DECLARE]], [[SUB]], [[FUNCTION]]
+
* DECLARE, [[SUB]], [[FUNCTION]]
 
* [[DIM]], [[_DEFINE]]
 
* [[DIM]], [[_DEFINE]]
 
* [[DEFSTR]], [[DEFLNG]], [[DEFINT]], [[DEFSNG]], [[DEFDBL]]
 
* [[DEFSTR]], [[DEFLNG]], [[DEFINT]], [[DEFSNG]], [[DEFDBL]]
 +
* [[INTEGER]], [[LONG]], [[_INTEGER64]]
 
* [[ABS]], [[SGN]]
 
* [[ABS]], [[SGN]]
 
* [[Variable Types]]
 
* [[Variable Types]]

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



Navigation:
Keyword Reference - Alphabetical
Keyword Reference - By Usage
Main Wiki Page