Page 15 - Sample_test_Float

Functions and Pointers 15

Example
void *ptr;
Consider the below example to clearly understand the void pointer:

void *ptr;// ptr is declared as Void pointer
char cnum;
int inum;
float fnum;
ptr = &cnum;// ptr has address of character data
ptr = &inum; // ptr has address of integer data
ptr = &fnum;// ptr has address of float data

Explanation
We have declared three variables of integer,character and float type.

• When we assign address of integer to the void pointer, pointer will become Integer Pointer.
• When we assign address of Character Data type to void pointer it will become Character Pointer.
• When we assign address of floating point Data type to void pointer it will become floating point Pointer
• It is capable of storing address of any data type

5.2.12. Null Pointer
• A pointer which does not point to any memory location is called NULL Pointer.

Meaning of NULL
• NULL is macro constant which has been defined in the header file stdio.h, alloc.h, mem.h, stddef.h and
stdlib.h as #define NULL 0

Example

int *a;
int *b = NULL;
here ‘*a’ and ‘*b’ are not same because b points to NULL and a may point to some garbage address

(a == b) FALSE, in most cases
(a == NULL ) FALSE, in most case
(b == NULL ) ALWAYS true
Example program:
Void main()
{
int *a;
int *b =NULL;
printf(“value of a =%d \t value of b =%d”,a,b);
}
Output:
Value of a = 28620 value of b = 0

NULL is a reserved word in most high-level languages. It is an EXPLICIT value, and not an”undefined”value.