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Logical
Operators

Run your mouse over the
panel at the left to see information about the logical operators.

A single
comparison in an if
statement often is not enough to determine whether data matches your
criteria. For example, you may need to check to see if a user
enters a number with a certain range. To accomplish this task, you
will need the logical operators in your
if statement.
These
logical operators which result in a
true/false condition are also
referred to as Boolean
Operators. 
It's
time to remember those truth tables from Mathematics! 
&&
(AND) 

(3 + 2 = 5)
&& (6 + 2 = 8) TRUE 

(4 + 3 = 9)
&& (3 + 3 = 6) FALSE 

 (OR) found above
the backslash on the keyboard 

(3 + 6 = 2)  (4
+ 1 = 5) TRUE 

(1 + 1 = 3)  (3
+ 3 = 9) FALSE 
!
(NOT) 

!(4 + 3 =
5) TRUE 

BEWARE:
Math:
2 < x < 10
OK
Computer: if (2
< x < 10) NO!!!
Will only do the
first condition.
if ((2 < x) && (x <
10)) YES 


Remember DeMorgan's Laws: 
Mathematical Version: 
Programming Version: 


Equivalent statements:
if (!(num >= 0 && num <= 65))
if (num < 0  num > 65) 
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