But, the homeworks are drawn from previous exams. So, I highly recommend that you take the homeworks seriously. Spend some time on the key problems before you consult with your friend or us. But, if you do have difficulty in completing a problem or understanding a posted solution, by all means consult us. Note the reading assignments.
System calls for files, directories.
System calls for protection and processes. Read Rochkind Chapters 3,5. System calls for interprocess communication, signals. Read Rochkind Chapters 6,8. Read Tanenbaum 2.1, 2.4.