When I use a

When I use a direct manipulation system whether for text editing, drawing pictures, or creating and playing games I do think of myself not as using a computer but as doing the particular task. The computer is, in effect, invisible. The point cannot be overstressed: make the computer system invisible. Donald A. Norman

On two occasions I

On two occasions I have been asked, ‘Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?’ I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question. Charles Babbage