Syscalls implemented and sample programs for each

1. lisproc(void)
- Prints the list of processes in the process table.
- Prints the time of launch
	Sample := ps.c

2. dumplog(void)
- Prints the runtime and launch time of the last 10 processes.
	Sample := dlog.c

3. trace(int)
- When 1 is used as argument , any subsequent syscall made by the process is displayed in the  	 console.
- When 0 is used as argument , the trace output stops.
	Sample := trace.c

4. datetime(struct rtcdate*)
- Fills in date and time information on the given rtcdate struct.
	Sample := date_eg.c

5. ppoint(int*)
- Displays the physical address of a given virtual address.
	Sample := ppoint.c

6. extend_as(int)
- Extends the virtual adresspace to the given new size.
	Sample := ext.c

7. dup2(int, int)
- Creates an alias file descriptor for a file that is open.
	Sample := dup2.c

8. yield(void)
- Calling process gives up the CPU.
	Sample := cpuno.c

9. alarm(int, void (*handler)())
- Executes a handler function in the process periodically depending on the argument provided.
	Sample := alarm.c

10. printproc(int)
- Print the process control block contents of a process with given pid.
	Sample := printproc.c

11. cpuno(void)
- Returns the currently running cpu.
	Sample := cpuno.c

12. lockcpu(int)
- Locks the calling process to a cpu specified in the argument.
	Sample := cpuno.c

13. unlockcpu(void)
- Unlocks the process from the current cpu.
	Sample := cpuno.c