Encyclopedia of Computer Science and Technology

A c k no w l e d g m e n t swish to acknowledge with gratitude the patient and thoroughI management of this project by my editor, Frank K. Darmstadt. I canscarcely count the times he has given me encouragement and nudgesas needed. I also wish to thank Tobi Zausner, Ph.D., for her ability andefficiency in obtaining many of the photos for this book.iv