Question

Consider the following ANSI C program:

#include <stdio.h>
#include <stdlib.h>
struct Node
{
int value;
struct Node *next;
};
int main( )
{
struct Node *boxE, *head, *boxN;
int index = 0;
boxE = head = (strcut Node *) malloc(sizeof (struct Node));
head $\to$value = index;
for (index = 1; index <=3; index++){
boxN = (struct Node *) malloc (sizeof (struct Node));
boxE $\to$ next = boxN;
boxN $\to$ value = index;
boxE = box N;}
for (index = 0; index <= 3; index ++)
{
printf("Value at index %d is %d\n", index, head $\to$value);
head = head $\to$ next;
printf("Value at index %d is %d\n", index + 1, head $\to$ value);
}
}

Which one of the statements below is correct about the program?

• A. It has a missing return which will be reported as an error b the compiler.
• B. It dereferences an uninitialized pointer that may result in a run-time error.
• C. Upon execution, the program goes into an infinite loop.
• D. Upon execution, the program creates a linked-list of five nodes

Answer 1

The correct option is B It dereferences an uninitialized pointer that may result in a run-time error.

As we can in the loop, i runs from 1 to 3.

So, four nodes will be created because one node is already created with value 0.


When index = 3, then head value = 3
Head = Head $\to$ Next (Now head will point to NULL)
Head $\to$ Value [which is in print. So it will generate Run time Error]

So, option (c) is correct.