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A pointer is a memory address that points to a specific piece of data or object, depending on the features of the language one is speaking about. A null value is a concept that represents an abstract type of data meaning "no data" or "unknown data," and is distinct from values such as 0, or "", which is data that is known to be "nothing."
A null pointer, then, is a pointer which has no data, meaning it has not been initialized to any specific value, and therefore unknown. In some languages, null pointers will cause exceptions, such as a NullPointerException, that can be handled by "error handling" mechanisms, while in other languages, access may be allowed to that pointer, potentially accessing system information or invalid memory addresses, causing the application or system to crash as memory is corrupted.
Modern operating systems have little chance of a system crash, but a null pointer exception that isn't handled will result in a General Protection Fault in Windows, and similar error conditions on other operating systems.
What else can I help you with?
What is the difference between equals 0 and equals NULL?
NULL is for pointers, 0, for numbers
Solution to null pointer assignment error?
Answer#ifndef NULL# define NULL ((void*)0)#endifAnswerDon't use pointers that contain NULL-value. Eg:int *myptr= NULL;...*myptr = 32; /* wrong */
Java does not support pointers then what is null pointer exception?
A null pointer exception is thrown when you are trying to manipulate an object that is null. It is just the name and does not have any relevance to the pointers as in C Example: ArrayList lst = null; Object obj = lst.get(0); In the first line we have declared an array list. Without initializing it we have tried to access the element in the 0th position. This would cause a null pointer exception.
How do you initialise pointers in functions?
Just like any other variable. Example: char *p = NULL;
Explain in detail in a binary tree of n nodes there are n plus 1 null pointers representing children?
Induction: 1. A tree of one node has two NULL-pointers. 2. Whenever you add a node to a tree, you remove one NULL-pointer (from the parent of the new node), and add two (the child's of the new node) in the same time.
What is the difference between null and void pointers?
A void pointer is a pointer that has no type information attached to it.A null pointer is a pointer that points to "nothing". A null pointer can be of any type (void included, of course).
Does failing to reject null mean null is true?
NO!
Difference between void pointer and null pointer?
A Null pointer has the value 0. void pointer is a generic pointer introduced by ANSI. Before ANSI, char pointers are used as generic pointer. Generic pointer can hold the address of any data type. Pointers point to a memory address, and data can be stored at that address.
What are the advantages of pointers in a program?
A pointer is simply a variable that stores a memory address and that allows that memory to be dereferenced. Unlike a reference, which must always refer to the object assigned to it, a pointer can refer to any object of the pointer's type, including null. A null pointer is simply a pointer that does not refer to any object. In languages that do not support pass by reference (such as C), pointers must be used to pass objects to functions. The pointer is passed by value, but the value is a memory address, which is the same as passing the object at that address. In languages that do support references (such as C++), references are useful when you need to guarantee an object exists because a reference can never be null. However, when passing an object to a function as an optional parameter, you must use a pointer because pointers can be null. Programmers must test pointers to ensure they are non-null before attempting to dereference them. References do not need to be tested; if a reference exists, it must refer to an object in memory.
What is the value of the un initialized pointers?
Random garbage, obviously. Let's note that global (ie not automatic) variables are automatically initialized by zero (=NULL)
How binary tree is represented as doubly link list?
In this representation, each node contains two pointers, one pointing to its parent (null in the case of root node) and the other pointing to its child node (null in the case of leaf nodes).
What does the error 'Null Pointer Assignment' mean?
The null pointer assignment error means your program has attempted to access a memory address that does not belong to your program. This typically occurs when accessing memory indirectly through a pointer: int* p = nullptr; *p = 42; // Error: null pointer assignment The above is the classic example of this type of error. The null address is typically the all-zeroes address (0x0) but, regardless of the physical address, it must never be accessed because it is a system address. We typically refer pointers to the null address when they are no longer in use or we don't have an address we can (yet) assign to them. Passing unchecked pointers to functions is another common cause: void f (int* p) { *p = 42; // potential error // ... } In the above example there's no guarantee p refers to a non-system address. Although we can easily test p is non-null before accessing it, that won't guarantee p refers to a non-system address. However, we can greatly reduce the risk of error by passing memory address via references instead of pointers: void f (int& r) { r = 42; // ... } There's still potential that r refers to a system address if the address were passed via a pointer, however there is seldom any need to use unchecked pointer variables in C++. References and resource handles (or smart pointers) eliminate the need for pointers and are actually more efficient than pointers because testing for null becomes largely redundant. The only time we really need a pointer is when "no object" is a valid argument: void f (int* p) { if (p == nullptr) { // the "no object" code } else { // code that operates on an object } }
