Computer Systems Colloquium
"Onwards to the Year 2000"
3.30 pm, Thursday 16 December
Room 2511, James Clerk Maxwell Building
Abstract
The "Y2K" problem has attracted much attention in recent years. The
concern is that, where the year in a date is stored using only two
decimal digits, moving from 1999 (99) to 2000 (00) might cause confusion,
for example, software believing that it has been plunged back to the
year 1900. In this pre-Christmas talk, a variant of the problem is
introduced and briefly examined: the Y2K Nibble Carry Problem. Suppose
that BCD arithmetic results in the value 99 being advanced to 100,
i.e., an extra BCD digit is generated. We identify two variants:
(a) the American-date big-endian problem, where the carry nibble
interferes with the last nibble of data stored before the date; and
(b) the European-date little-endian problem, where the carry nibble
interferes with the first nibble of data stored after the date. The
implications for some example unluckily-trampled data types will be
outlined. The audience will be invited to contribute their own
examples, in a Christmas party game-style scenario. Mince pies will
be served afterwards.
Last modified: Mon Dec 6 09:23:30 GMT 1999
Please contact our
webadmin with any comments or changes.
Unless explicitly stated otherwise, all material is
copyright © The University of Edinburgh.
