Search results
Results from the WOW.Com Content Network
For example, in x86 real mode, the address 0000:0000 is readable and also usually writable, and dereferencing a pointer to that address is a perfectly valid but typically unwanted action that may lead to undefined but non-crashing behavior in the application; if a null pointer is represented as a pointer to that address, dereferencing it will ...
A null pointer has a value reserved for indicating that the pointer does not refer to a valid object. Null pointers are routinely used to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type .
It is often abbreviated as NUL (or NULL, though in some contexts that term is used for the null pointer). In 8-bit codes, it is known as a null byte. The original meaning of this character was like NOP—when sent to a printer or a terminal, it has no effect (some terminals, however, incorrectly display it as space).
A straightforward example is shown below: { char * dp = NULL ; /* ... */ { char c ; dp = & c ; } /* c falls out of scope */ /* dp is now a dangling pointer */ } If the operating system is able to detect run-time references to null pointers , a solution to the above is to assign 0 (null) to dp immediately before the inner block is exited.
Dereferencing a null pointer and then assigning to it (writing a value to a non-existent target) also usually causes a segmentation fault: int * ptr = NULL ; * ptr = 1 ; The following code includes a null pointer dereference, but when compiled will often not result in a segmentation fault, as the value is unused and thus the dereference will ...
For example, if you have a dog breed that’s made for running, like an aerodynamic sighthound or an energetic springer spaniel, the new year could be the time to take up running together.
Null pointer for indicating the end of a linked list or a tree. A set most significant bit in a stream of equally spaced data values, for example, a set 8th bit in a stream of 7-bit ASCII characters stored in 8-bit bytes indicating a special property (like inverse video, boldface or italics) or the end of the stream.
For example, oil might undergo a bleaching and refining phase to remove any odors and colors, but that doesn't mean you're finding bleach in your oil.