Logical Operator
When we use if, for, while then use one condition at once
time what happen if we examine condition more than one? In this case we use
logical operators. So logical operators are used to combine two or more
condition.
There are three types of logical operators as following:
There are three types of logical operators as following:
Operator
symbol
|
Name
|
&&
|
Logical AND
|
||
|
Logical OR
|
!
|
Logical NOT
|
· LOGICAL AND OPERATOR ( && )
The condition is true if and only if both two expression are
true otherwise condition false. The truth table of logical AND operators end of
this chapter.
· LOGICAL OR OPERATOR ( || )
The condition is true if one of expression is true and
condition will be false only if both expression are false. See example of ||
operator at end of this chapter.
· LOGICAL NOT OPERATOR ( ! )
It reverse the expression i.e if the expression
evaluates to a non-zero value, then applying ! operator to it results
into a 0 and vice versa. The final result (after applying ! ) 0 or 1 is
considered to be false or true respectively.
Example of above three operators :
//following
table con = condition.
con
1
|
Con
2
|
con
1 && con 2
|
con
1 || con 2
|
! con 1
|
!
con 2
|
False
|
False
|
False
|
False
|
True
|
True
|
False
|
True
|
False
|
True
|
True
|
False
|
True
|
False
|
False
|
True
|
False
|
True
|
True
|
True
|
True
|
True
|
False
|
False
|
Some numerical example :
if(10>5
&& 1000<2001) // True
while( ;
num>=1 || num<=100 ; ) // if
num=1 True
Now some discuss of NOT operator when we write
condition if( 1 ! = 0 ) what is mean it? It
is mean "one is not equal to zero",
so is condition TRUE or False? It is true.
Let's understand following example :
if(sex!='M')
printf("Person is
Female");
else
printf("Person is
Male");
In above example evaluate first printf if condition is false
otherwise evaluate second printf.
!(x<22) it is also we write (x>=22) // both are equal.
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