c_programming

Question

#include "stdio.h"

 int * gPtr;

int main()
{
int * lPtr = NULL;

if(gPtr == lPtr)
{
printf("Equal!");
}
else
{
printf("Not Equal");
}

return 0;
}

what will be the outpout :

A.> it will always print equal

B> it will always print Not equal

C>Since gPtr isn’t initialized in the program, it’ll print sometimes Equal and at other times Not Equal.

Comments

(C)?

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I think global pointers are always initialized to null.

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@saxena0612  that is true, but how will the comparison be done .

*something =a, that means  if we print  or compare something then that will give address of "a". here lptr = null so how is gonna be compared . :(

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nope , answer is "a"

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My confusion is :

Global pointer *gPtr will take some space in Static area, where  *Lptr scope is within the main function so it will take some space in stack area of memory. now when we write pointer variable name only  that  refers to pointing address . so how can  the if condition be true , where the   pointing address is not the same ??

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@bharti let me clear you confusion basically when you point pointer to NULL then it means that it is pointing to the memory address 0x0.
0x0 is the address of NULL value i.e. 0. You cannot access 0x0 memory address.

Now if you compare two pointers which are pointing to memory address 0x0 i.e. NULL then it will be same only as the NULL value is 0 by default

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@saxena0612

okk so u mean to say no matter  it is global  assignment  or local assignment of null  , both will point to Same address  0x0  . that  is the reason of condition  being true .

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Yup ! compile their address for better understanding!

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@saxena0612

yeah ! I did :)

Thank you

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@saxena0612

Any resources for your this statement.

"when you point pointer to NULL then it means that it is pointing to the memory address 0x0." (Always)

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According to C Standard Document section 6.3.2.3:

An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant.55) If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.

Answer 1

Ans is A.

Global variables (pointers or data members) are always assigned a default value at compilation. Hence the default value for gPtr is NULL.

Answer 2

Global variables are by default NULL and the ASCII value of NULL is 0.So 0=0 is true hence output would be EQUAL!