//c program to perform following system calls

File structure related system calls:
               1.creat()
               2.open()
               3.close()
               4.read()
               5.write()
               6.lseek()
               7.dup()
               8.link()
               9.unlink()
               10.access()
               11.chmod()
               12.chown()
               13.umask()
               14.ioctl()


Process related system calls
               1.execl()
               2.fork()
               3.wait()
               4.exit()
               5.getuid()
               6.geteuid()
               7.getgid()
               8.getegid()
               9.getpid(),
               10.getppid()
               11.signal()
               12.kill()
               13.alarm()
               14.chdir()