What does while(*pointer) means in C?

Question

When I recently look at some passage about C pointers, I found something interesting. What it said is, a code like this:

char var[10];
char *pointer = &v         


        

Answer 1

Let's start with a simple example::

int a = 2 ;
int *b = &a ;
/* Run the loop till *b i.e., 2 != 0 
Now, you know that, the loop will run twice 
and then the condition will become false 
*/
while( *b != 0 )
{
 *b-- ;
}

Similarly, your code is working with char*, a string.

char var[10] ;
/* copy some string of max char count = 9, 
and append the end of string with a '\0' char.*/
char *pointer = &var ;
while( *pointer != '\0' )
{
 // do something
 // Increment the pointer 1 or some other valid value
}

So, the while loop will run till *pointer don't hit '\0'.

while( *pointer )
/* The above statement means the same as while( *pointer != '\0' ),
because, null char ('\0') = decimal value, numeric zero, 0*/

But the usage can change when you do, while(*pointer != 'x'), where x can be any char. In this case, your first code will exit after *pointer hits the 'x' char but your second snippet will run till *pointer hits '\0' char.