The memoirs that have come out of Africa are sometimes startlingly beautiful often urgent and essentially life-affirming but they are all performances of courage and honesty.

And as a child I was filled with passionate admiration for acts of civic courage I had seen performed by an elderly military doctor who was a friend of my family.

When you see people who are really good at game shows the one common attribute is a cool head under pressure: an ability to perform as well in the studio surrounded by lights and noise as you do on your couch.

Eventually I believe current attempts to understand the mind by analogy with man-made computers that can perform superbly some of the same external tasks as conscious beings will be recognized as a gigantic waste of time.

China has legally purchased high performance computers advanced machine tools and semiconductor-manufacturing equipment from several American companies.

Man-made computers are limited in their performance by finite processing speed and memory. So too the cosmic computer is limited in power by its age and the finite speed of light.

Our lives sometimes depend on computers performing as predicted.

In the practical world of computing it is rather uncommon that a program once it performs correctly and satisfactorily remains unchanged forever.

Home computers are being called upon to perform many new functions including the consumption of homework formerly eaten by the dog.

Without a possibility of change in meanings human communication could not perform its present functions.