Pointers defined using specific data type cannot hold the address of the some other type of variable i.e., it is incorrect in C++ to assign the address of an integer variable to a pointer of type float.

Example:

float *f; //pointer of type float
int i;  //integer variable
f = &i; //compilation error

The above problem can be solved by general purpose pointer called void pointer.

Void pointer can be declared as follows:

 
void *v // defines a pointer of type void

The pointer defined in this manner do not have any type associated with them and can hold the address of any type of variable.

Example:

void *v; 
int *i;
int ivar;
char chvar;
float fvar;
v = &ivar; // valid
v = &chvar; //valid
v = &fvar; // valid
i = &ivar; //valid
i = &chvar; //invalid
i = &fvar; //invalid

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