Logical and and or in C
In a && B, This Returns True If Both a and B Are Equal to 1. If A=-1 and B=-1 Then Also the Expression Returns True. Similar Is the Case with A||B, Where A=-1...
In a && b , this returns true if both a and b are equal to 1. If a=-1 and b=-1 then also the expression returns true.Similar is the case with a||b,where a=-1 and b=0,it returns true. Can anybody please explain the reason.
6 Answers
a && b returns 1 when both a and b are nonzero, not just when they're equal to 1. Otherwise it returns 0.
a || b returns 1 when at least one of a or b is nonzero, not just when one of them is equal to 1. Otherwise it returns 0.
To give some examples:
0 && 0 -> 0
1 && 0 -> 0
1 && 1 -> 1
2 && 1 -> 1
-1 && -1 -> 1
-100 && 0 -> 0
0 || 0 -> 0
1 || 0 -> 1
0 || 1 -> 1
-1 || 0 -> 1
-100 || 20 -> 1
C11 (n1570) §6.5.13 al 3 p 99 say :
The && operator shall yield 1 if both of its operands compare unequal to 0; otherwise, it yields 0.
-1 is a nonzero value, so -1 && -1 is 1.
On the MSDN page for &&:
The logical-AND operator produces the value 1 if both operands have nonzero values.
Clearly both operands are -1 in your example so they will produce 1.
On the same page, listed for ||
If either operand has a nonzero value, the result is 1.
In your case one operand is -1, therefore the result is 1
AND returns 1 if both operands have non-zero values. OR returns 1 if either operand has a non-zero value.
and operator i.e (&&) will proceed only if both the conditions are true , wheree as in the case of or operator i.e(||) will proceed if atleast one of he two condition is true..
Logical operators return either 0 or 1. The && operator returns 1 if both its operands are not 0.Else,it return 0. statements like if(x),while(x) etc.. get executed if its argument is not 0.For all other +ve and -ve arguments it get executed.
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