What is the value of a null pointer?

What is the value of a null pointer?

0
A null pointer constant is an integer constant expression that evaluates to zero. For example, a null pointer constant can be 0, 0L , or such an expression that can be cast to type (void *)0 .

What is null and void pointer?

A null pointer points has the value NULL which is typically 0, but in any case a memory location which is invalid to dereference. A void pointer points at data of type void. The word “void” is not an indication that the data referenced by the pointer is invalid or that the pointer has been nullified.

Is a null pointer 0?

The null pointer constant is always 0. The NULL macro may be defined by the implementation as a naked 0 , or a cast expression like (void *) 0 , or some other zero-valued integer expression (hence the “implementation defined” language in the standard). The null pointer value may be something other than 0.

How do you check if a pointer is empty?

An integer literal with value zero (including 0 and any valid definition of NULL ) can be converted to any pointer type, giving a null pointer, whatever the actual representation. So p != NULL , p != 0 and p are all valid tests for a non-null pointer.

Is void and null same?

The difference between null and void as term for nothing stems from their place in physical space. A void is nothing but takes up space; null is nothing at all. In other words, you could measure a void but null offers nothing to measure. 4.1 Void is used to indicate that a function/method does not return any data type.

Does null exist in C?

Null is a built-in constant that has a value of zero. It is the same as the character 0 used to terminate strings in C.

How do I know if a pointer is pointing to null?

Since NULL is zero, an if statement to check whether a pointer is NULL is checking whether that pointer is zero. Hence if (ptr) evaluates to 1 when the pointer is not NULL, and conversely, if (! ptr) evaluates to 1 when the pointer is NULL.

Why do I get a NullPointerException?

Calling the instance method of a null object.

Accessing or modifying the field or a null object.

Taking the length of the null as if it were an array.

Accessing or modifying the slots of null as if it were an array.

Throwing null as if it were a Throwable value.

What does null pointer mean?

Pointer is a programming language object, whose value refers to (or “points to”) another value stored elsewhere in the computer memory using its address. So, a Null Pointer is a Pointer whose value refers to Nowhere in the Memory.

What does the error ‘null pointer assignment’ mean?

error null pointer assignment when we initialize any pointer to null that mean not point to any thing now if we are trying to access mean use or try to put some value to it then the error null pointer assignment occur.

What is an invalid pointer?

An invalid pointer reference occurs when a pointer’s value is referenced even though the pointer doesn’t point to a valid block. One way to create this error is to say p=q;, when q is uninitialized. The pointer p will then become uninitialized as well, and any reference to *p is an invalid pointer reference.