system_calls = { 'fork': 'creates a duplicate of the process with both processes being identical except for the return value from fork', 'execv': 'replaces the program code for the current process with program code from a file', 'open': 'open and possibly create a file', 'close' :'close a file descriptor (could be a file or socket)', 'read' : 'read from a file descriptor (could bea file or socket', 'write' : 'write to a file descriptor (could be a file or socket)', 'unlink' : 'remove reference to a given file from a directory (similar to rm, rm is based on this)' }