Some computers do not provide a privileged mode of operation in Hardware, is it possible to construct a secure O/S for these computers? Why and Why not? Please I need a feedback. I know it is possible to construct a secure O/S because the operating sys. can create a security system to protect the processes but I don't know why not.

You are asking the wrong kind of question (please read the Announcements) and in the wrong forum (this is C++ Software Development, not the Tech Talk forum).

Please spend some time with your textbook, googling, and thinking about the concepts you have learned so far. I doubt your professor will want a highly detailed, super-technical answer.

What kind of things can you do to protect security?
What kind of things can you do to get around security?

Non-privileged mode operating systems are probably just too small to accommidate all the code needed to protect the hardware from damaging programs. For example MS-DOS 6.X and earlier were already limited to using 640K of memory, and that had to include the operating system and all TSRs, which left most application programs just 450K or so RAM. Now add code to the os to prptect the hardware and there would be little, if any, RAM left.

Thanks for your response. I knew it was a security issue I just wanted better ideas than what I read in the text book. Thanks again.