Question:What is NULL pointer? 

Answer Explanation:
Literal meaning of NULL pointer is a pointer which is pointing to nothing. NULL pointer points the base address of segment.

Examples of NULL pointer:
1. int *ptr=(char *)0;
2. float *ptr=(float *)0;
3. char *ptr=(char *)0;
4. double *ptr=(double *)0;
5. char *ptr=’\0’;
6. int *ptr=NULL;
What is meaning of NULL?
Answer:

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

Examples:

(1) What will be output of following c program?
#include "stdio.h"
int main(){
if(!NULL)
printf("I know preprocessor");
else
printf("I don't know preprocessor");
}
Output: I know preprocessor

Explanation:
!NULL = !0 = 1
In if condition any non zero number mean true.

(2) What will be output of following c program?
#include "stdio.h"
int main(){
int i;
static int count;
for(i=NULL;i<=5;){
count++;
i+=2;
}
printf("%d",count);
}
Output: 3

(3) What will be output of following c program?
#include "stdio.h"
int main(){
#ifndef NULL
#define NULL 5
#endif
printf("%d",NULL+sizeof(NULL));
}
Output: 2

Explanation:
NULL + sizeof(NULL)
=0 + sizeoof(0)
=0+2 //size of int data type is two byte.

We cannot copy anything in the NULL pointer.

Example:

(4) What will be output of following c program?
#include "string.h"
int main(){
char *str=NULL;
strcpy(str,"c-pointer.blogspot.com");
printf("%s",str);
return 0;
}
Output: (null) 

+ Report

Mohammad Towhidul Islam

Editor, VCampus

Your Name

Your Email

Type of Report
Spelling MistakeIncorrect AnswerGrammar MistakeContent MissingImproper Text FormatInsufficient AnswerDuplicate QuestionImproper Sentence StructureImproper Equation/FormulaOther

Description