Consider Peterson’s algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below.

 Repeat 
     flag[i]=true; 
     turn=j; 
     while (P) do no-op; 
     Enter critical section, perform actions, then 
     exit critical section 
     Flag[i]=false; 
     Perform other non-critical section actions. 
 Until false;

For the program to guarantee mutual exclusion, the predicate P in the while loop should be

Consider the following three C functions:

[P1] int*g(void)
     {
       int x=10;
       return(&x);
     }

[P2] int*g(void)
      {
        int *px;
       *px = 10;
        return px;
      }

[P3] int*g(void)
     {
       int *px
       px =(int*)malloc (size of (int));
       *px = 10;
       return px;
     }

Which of the above three functions are likely to cause problems with pointers?

Consider the following C program:

void abc(char *s)
{
   if(s[0]=='\0') return;
   abc(s+1);
   abc(s+1);
   printf("%c",s[0]);
}
main()
{ 
   abc("123");
}

(a) What will be the output of the program?
(b) If abc(s) is called with a null-terminated string s of length n characters (not counting the null ('\0') character), how many characters will be printed by abc(s)?

What is printed by the print statements in the program P1 assuming call by reference parameter passing?

Program P1()
{
     x=10;
     y=3;
     func1(y,x,x);
     print x;
     print y;
}
func1(x,y,z)
{
     y=y+4;
     z=x+y+z;
}