They are pointers without type
Data-type void has some special features:- it doesn't have values- it doesn't have size- you cannot declare variables with it- void *pointers cannot be dereferenced
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).
It is not possible to declare a two-dimensional array using an array of pointers in any programming language, but many programming languages support declarations of N-dimensional arrays of pointers.The exact syntax varies with the programming language, and requires support for N-dimensional arrays and pointers. In C, the following declares an array of pointer variables, each implemented as pointer to the generic type "void":void* array_1D[10];The type of the expression array_1D is "void * const."The following example expands on the previous one by declaring a two-dimensional array of "void" pointers:void* array_2D[10][20];The type of the expression array_2D is "void ** const."The last example declares a 3-dimensional array of "void" pointers, which can be seen as a 2-dimensional array of arrays of pointers:void* array_3D[10][20][30];
Example: int **myfun (void) { int **myptr= calloc (sizeof (int *), 100); return myptr; }
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.
Pointer to Pointer is a double pointer, denoted by (**). Pointer stores the address of the variable and pointer to pointer stores the address of a pointer variable and syntax can be given as int **ptr2ptr;
Void - is empty data type in C
... are usable. void pointer (generic pointer) : a special type of pointer which point to some data of no specific types. void *p; null pointer : a special type of pointer which point nowhere. it is usually used to check if a pointer is pointing to a null or free the pointer during deallocation of memory in dynamic memory allocation; it is define by using the predefine constant NULL int *p=NULL; wild pointer : uninitialized pointer. it hold a garbage value. i.e it is not pointing to any memory location yet. dangling pointer: pointer pointing to a destroyed variable. it usually happen during dynamic memory allocation when the object is destroyed but not free and the pointer is still pointing to the destroy object.
using pointers, example: void Swapd (double *d1, double *d2) { . double tmp= *d1; . *d1= *d2; . *d2= *tmp; }
The voiddata type is used when a function doesn't return any value, and/or when it has no parameters at all. Pointer type 'void *' is a generic pointer.A void pointer is used when it needs to be assigned to different data types later on in a program. Since it avoids type checking, void pointers should be used with care.
Answer#ifndef NULL# define NULL ((void*)0)#endifAnswerDon't use pointers that contain NULL-value. Eg:int *myptr= NULL;...*myptr = 32; /* wrong */
what is void data type Void is an empty data type normally used as a return type in C/C++, C#, Java functions/methods to declare that no value will be return by the function. The another use of void is to declare the pointer in C/C++ whe It is not sure that what data type will be addressed by the pointer. eg: void *p; Here p can hold the address of int or float or char or long int or double.