DESIRABLE QUALITIES OF OS

 DESIRABLE QUALITIES OF OS

The desirable qualities of an operating system are in terms of: Usability, Facilities, Cost, and Adaptability.

• Usability: 

         • Robustness

         • Accept all valid inputs and can handle them.

         • Consistency

         • Proportionality

         • Convenience

         • Powerful with high level facilities.

 • Facilities:

        • Sufficient for intended use

         • Complete

         • Appropriate.

• Costs:

         • Want low cost and efficient services.

         • Good algorithms.

        Make use of space/time tradeoffs, special hardware.

         • Low overhead. 

         Cost of doing nothing should be low. E.g., idle time at a terminal.

         • Low maintenance cost. 

         System should not require constant attention

• Adaptability:

         • Tailored to the environment.

         Support necessary activities. Do not impose unnecessary restrictions.

         What are the things people do most -- make them easy.

     • Changeable over time. 

     Adapt as needs and resources change. e.g., expanding memory and new devices, or new user                 population.

     • Extendible-Extensible 

     Adding new facilities and features - which look like the old ones.