Logical NOT operator : True and false condition
A ~A
0 1
1 0
If A = 0 then condition become true if A = 1 then condition become falseCode:#include <stdio.h> int main (void) { unsigned int A = 1; if (!A) { printf (" True"); } else { printf ("False"); } return 0; }
what is meaning of this if(!A) ?
When found inside a boolean expression, an integer is equivalent to False if zero and True otherwise. So in your code, "!A" essentially means "A == 0".
Devoted my life to programming...
I don't perceive much of a question here, but I'll do my best to guess at it.
Actually, 0 is always false and anything else is always true. Some functions return 0 in some circumstances and it may be those circumstances where you want to do something. For example, if you are using the function strcpy(char* a, char* b), this function returns 0 if a is equal to b. If you want to do something when a is not equal to b, you might use the logical not operator.
However, I think you might be assuming ! and ~ are the same thing. The ! is the logical not operator while ~ is the bitwise not operator. The bitwise not operator flips all bits that are one's to become zeros and all zeros to become ones. The logical not changes any non-zero decimal number (not bits) to become zero and any zero value to become one.Code:if (!strcpy(a, b)) { // do something }
Last edited by jack jordan; 10-27-2017 at 01:29 AM.
Thanks @GReaper and @Jack jordan
What is meaning of logic not (!) in defineCode:#include <stdio.h> int main (void) { unsigned int A; printf("Enter Input"); scanf("%d", &A); if (!A) { printf (" True"); } else { printf ("False"); } return 0; }
#define low (!low)
#define low (!High)
I just saw I made a mistake, which seems to happen all the time. When I wrote strcpy, I meant strcmp.
IF the user did input some value into the variable then the if expression becomes false and in this case the else portion of the code is printed.
In essence if the variable has a value, the not operator makes the expression which should be true false which then leads the the printing out of the else statement.
