Reliability is that a system does exactly what is it designed to do.
At software level OS must be more reliable on detecting VIRUSES or MALICIOUS CODES as they take control of the system for their own purposes by exploiting design or implementation errors in the operating system's defenses.
It is the percentage of time that a system is usable. Some systems crashes frequently, loosing the users work. Both Reliability and Availability are desirable.
Availability is effected by 2 factors:
• The frequency of failure called the 'Mean Time To Failure(MTTF)' and the time it takes to restore a system to a working state after failure (For example, to reboot ), the MTTR(Mean Time To Repair)
• Availability can be improved by increasing the MTTF or reducing the MTTR.
Ease of Management:
Operating system must be easy to manage as there are lots of help and tutorials are available to rectify the errors.
As Operating System has administrative users that can make changes to the computer but for other user to make changes he has enter the password for administrative account.
Associated Utilities :
operating System have lots of associated utilities available like windows Operating System has lots of versions and according to their version lots of free utilities are available like MS-Office, MS-SQL, Developing Languages.
Operating System cost should be accordance of its features like windows has around $100 where DOS is free of charge as so is UNIX.
Support for users :
Operating System have help section for Users if any error, any problem occurs like windows has proper help sections and websites.
Where LINUX has books in PDF format available and DOS has websites and Forum for help as DOS is not much popular.
02-Operating System Characteristics - Operating System