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What will be the output of the below code? the answer given is E)0 but I am not getting it.
 

#include <stdio.h>
void fun(short int *a,char *b)
{
    b += 2;
    short int *p = (short int*)b;
    *p = *a;
}


int main()
{
    void (*fptr)(short int *,char *)
    short int a = 101;
    char arr[] = {'a','b','c','d'};
    fptr = fun;
    (*fptr)(&a,arr);
    printf("%d", arr[3]);

    return 0;
}


$A)$ Compilation error.

$B) 100$

$C)$ Garbage Value

$D)$ Segmentation Fault.

$E) 0$

in Programming by (39 points)
edited by | 113 views

1 Answer

+1 vote
Best answer
 

go through these links before reading answer if these concepts are not clear

SO:

https://stackoverflow.com/questions/12279060/what-is-the-difference-between-short-int-and-int-in-c 

 

 

A[0](1000+0) A[1](1000+1) A[2](1000+2) A[3](1000+3)
a b c d

short int *p = (short int*)b;

what this line does is assigns address 1002 in "p" in such a way that it will take 2 bytes 1002 and 1003(since it takes 2 bytes)

Now, when we assign 101 to it because of little-endian format, the higher order byte having 0 will be placed in right (A[3]) and lower order byte having value 101 at A[2], What you can do to test this is run the same program with 300 O/P would be 1 because higher order byte has 1(requires 256) 

Endian 

https://www.geeksforgeeks.org/little-and-big-endian-mystery/

 

by Active (2k points)
edited by
0

Thanks @Anuj Mishra but, is it syntactically correct to assign fun to fptr?

0

Yes it is correct (function name itself is like an array name - so you can remove & and it still works - definitely go through this for reading and examples-http://www.cs.cmu.edu/~guna/15-123S11/Lectures/Lecture14.pdf

Also if  times, search wiki for function pointer - there you'll get a good example and some important usage too

0

@Anuj Mishra

Please Separate both the links in the post. They are showing as one url.

0

Thanks @logan1x , edited now.

0

@Anuj Mishra

Can u plz explain this line

fptr = fun;

Here fptr is a pointer, which should take address of 'fun'. Is it not?

0
Yes it is, read my above comment and go through link in that comment
0

How a function can be used as an array?

Even in array we use sign. isnot it?

0

No. We don't use & for referring whole array. Go through the first answer, same is case for functions ( please read above link if you haven't )

https://stackoverflow.com/questions/1641957/is-an-array-name-a-pointer

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