QB64-PE/internal/help/NOT.txt

'''NOT''' is a [[Boolean]] logical operator that will change a False statement to a True one and vise-versa. 


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:: True = -1: False = '''NOT''' True


* In Qbasic, True = -1 and False = 0 in boolean logic and evaluation statements.
* NOT evaluates ONE value and returns the opposite. Yes, NOT 0 = -1 in Basic.
* Often called a negative logic operator, it returns the opposite of a value as true or false.

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''Example 1:'' Alternating between two conditions in a program loop.
{{CodeStart}}
{{Cl|DO}}
switch = {{Cl|NOT}} switch       '{{Cl|NOT}} changes value from -1 to 0 and vice-versa
{{Cl|LOCATE}} 10, 38
{{Cl|IF}} switch {{Cl|THEN}} {{Cl|PRINT}} "True!" {{Cl|ELSE}} {{Cl|PRINT}} "False"
{{Cl|SLEEP}}
k$ = {{Cl|INKEY$}}
{{Cl|LOOP}} {{Cl|UNTIL}} k$ = {{Cl|CHR$}}(27) ' escape key quit
{{CodeEnd}}


''Example 2:'' Reading a file until it reaches the End Of File.
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DO WHILE NOT EOF(1) 
  INPUT #1, data1, data2, data3
LOOP '' ''
{{CodeEnd}}
:''Explanation:'' [[EOF]] will return 0 until a file ends. NOT converts 0 to -1 so that the loop continues to run. When EOF becomes -1, NOT converts it to 0 to end the loop.


''See also:'' 
*[[DO...LOOP]], [[WHILE...WEND]], 
*[[IF...THEN]], [[AND]], [[XOR]]
*[[OR]], [[Binary]], [[Boolean]] 
*[[Mathematical Operations]]


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