Computers are everywhere around us. We, for example, as air passengers,
car drivers, laptop users with Internet connection, cell phone owners,
hospital patients, inhabitants in the vicinity of a nuclear power
station, students in a digital library or customers in a supermarket are
dependent on their correct operation. Computers are incredibly fast,
inexpensive and equipped with almost unimag- able large storage
capacity. Up to 100 million transistors per chip are quite common
today - a single transistor for each citizen of a large capital city in
the world can be 2 easily accommodated on an ordinary chip. The size of
such a chip is less than 1 cm . This is a fantastic achievement for an
unbelievably low price. However, the very small and rapidly decreasing
dimensions of the transistors and their connections over the years are
also the reason for growing problems with reliability that will
dramatically increase for the nano-technologies in the near future. Can
we always trust computers? Are computers always reliable? Are chips suf-
ciently tested with respect to all possible permanent faults if we buy
them at a low price or have errors due to undetected permanent faults to
be discovered by c- current checking? Besides permanent faults, many
temporary or transient faults are also to be expected.
