GATE CS 2000 Q1.12 — Programming in C

We can determine the correct matching by analyzing each scenario step-by-step:

1. Scenario X: m = malloc(5); m = NULL;
   Memory of $5$ bytes is dynamically allocated on the heap, and its address is stored in the pointer m. When m is reassigned to NULL without freeing the allocated memory, the program loses the reference to that heap memory. This results in a memory leak, also known as lost memory.
   $$\text{Hence, } X \rightarrow 3$$
2. Scenario Y: free(n); n -> value = 5;
   The memory block pointed to by n is deallocated using free(n). After deallocation, n still holds the address of that memory block, making it a dangling pointer. Attempting to access or modify members using n->value is an operation on a dangling pointer.
   $$\text{Hence, } Y \rightarrow 1$$
3. Scenario Z: char *p; *p = 'a';
   The pointer p is declared but not initialized to point to any valid memory address (it contains a garbage value). Dereferencing it with *p = 'a' attempts to write to an arbitrary memory location, which is a classic case of using an uninitialized pointer.
   $$\text{Hence, } Z \rightarrow 2$$

Combining these matches, we get: $$\mathbf{X - 3, \quad Y - 1, \quad Z - 2}$$ This corresponds to Option D.