The atomic fetch-and-set x, y instruction unconditionally sets the memory location x to 1 and fetches the old value of x n y without allowing any intervening access to the memory location x. consider the following implementation of P and V functions on a binary semaphore S.

void P (binary_semaphore *s) { 

   unsigned y; 
   unsigned *x = &(s->value); 
   
   do { 

     fetch-and-set x, y; 

   } while (y); 
} 

void V (binary_semaphore *s) { 

   S->value = 0; 

} 

Which one of the following is true?

A Computer system supports $$32$$-bit virtual addresses as well as $$32$$-bit physical addresses. Since the virtual address space is of the same size as the physical address space, the operating system designers decide to get rid of the virtual memory entirely. Which one of the following is true?

Consider the following snapshot of a system running n processes. Process i is holding x_i instances of a resource R, for $$1 \le i \le n$$. Currently, all instances of R are occupied. Further, for all i, process i has placed a request for an additional y_i instances while holding the x_i instances it already has. There are exactly two processes p and q such that y_p = y_q = 0. Which one of the following can serve as a necessary condition to guarantee that the system is not approaching a deadlock?

Consider this C code to swap two integers and these five statements:

void swap(int *px, int *py) 
{ 
    *px = *px - *py; 
    *py = *px + *py; 
    *px = *py - *px; 
}

S1: will generate a compilation error

S2: may generate a segmentation fault at runtime depending on the arguments passed

S3: correctly implements the swap procedure for all input pointers referring to integers stored in memory locations accessible to the process

S4: implements the swap procedure correctly for some but not all valid input pointers

S5: may add or subtract integers and pointers.