WHAT IS null pointer and why it is used?

WHAT IS null pointer and why it is used?

A null pointer has a reserved value that is called a null pointer constant for indicating that the pointer does not point to any valid object or function. You can use null pointers in the following cases: Initialize pointers. Represent conditions such as the end of a list of unknown length.

What is the use of null pointer in C++?

It is always a good practice to assign the pointer NULL to a pointer variable in case you do not have exact address to be assigned. This is done at the time of variable declaration. A pointer that is assigned NULL is called a null pointer.

What are uses of null and void pointers?

Null pointer is used for assigning 0 to a pointer variable of any type. Void pointer is used for storing address of other variable irrespective of its datatype.

What happens when you set a pointer to null?

What happens here is that when a Null pointer is created, it points to null, without any doubt. But the variable of Null pointer takes some memory. Hence when a pointer to a null pointer is created, it points to an actual memory space, which in turn points to null.

Why do we use null?

Null or NULL is a special marker used in Structured Query Language to indicate that a data value does not exist in the database. SQL null is a state, not a value. This usage is quite different from most programming languages, where null value of a reference means it is not pointing to any object.

WHAT IS null pointer explain with example?

The word “NULL” is a constant in C language and its value is 0. In case with the pointers – if any pointer does not contain a valid memory address or any pointer is uninitialized, known as “NULL pointer”. We can also assign 0 (or NULL) to make a pointer as “NULL pointer”.

Why void pointer is used?

void pointers should be used any time the contents of a block of data is not important. For example when copying data the contents of a memory area is copied but the format of the data is not important.

Which pointer does not exist?

NULL Pointer is a pointer which is pointing to nothing.

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.

How do you use null?

Allow null only if it makes sense for an object reference to have ‘no value associated with it’. Don’t use null to signal error conditions. The concept of null exists only for reference types. It doesn’t exist for value types.

Is the null pointer same as an uninitialized pointer?

Using an uninitialized pointer is undefined behavior, but dereferencing a NULL pointer is also undefined behavior (both could lead to a crash). The difference is that an uninitialized pointer could be anything, but a NULL pointer has a definite value (i.e. NULL ).

What is the difference between null and void pointers?

Conceptually, when a pointer has that null value it is not pointing anywhere. Void pointer is a specific pointer type – void * – a pointer that points to some data location in storage, which doesn’t have any specific type. So, once again, null pointer is a value, while void pointer is a type.

Is null pointer is always zero?

It is always a good practice to assign the pointer NULL to a pointer variable in case you do not have exact address to be assigned. This is done at the time of variable declaration. A pointer that is assigned NULL is called a null pointer. The NULL pointer is a constant with a value of zero defined in several standard libraries, including iostream.

What does null pointer mean?

Null pointer. In computing, a null pointer or null reference has a value reserved for indicating that the pointer or reference does not refer to a valid object.