/* ****************BLOCK.H********
  Jonathan W. Valvano   Feb 26, 1997
  Spinlock semaphores */
#define null 0
struct	sema4
{   unsigned int value;
    struct TCB *BlockPt;   /* blocked on this */
};
typedef struct sema4 sema4Type;
typedef sema4Type * sema4Ptr;
void Wait(sema4Ptr);
void Signal(sema4Ptr);