[Year 12 SofDev] Overflow

[Mark KELLY]

A couple of interesting tales to tell the kids about overflowing a
variable's capacity, and the importance of choosing the right sized variable
for all current and future contingencies.

Found at www.cs.bgsu.edu/maner/ethicomp95/keynote3-THE.html

- A hospital computer system in Washington, D.C., broke down on September
19, 1989, because its calendar calculations counted the days elapsed since
January 1, 1900. On the 19th of September, exactly 32,768 days had elapsed,
overflowing the 16-bit word used to store the counter, resulting in a
collapse of the entire system and forcing a lengthy period of manual
operation.

- At the Bank of New York, a similar 16-bit counter overflowed, resulting in
a $32 billion overdraft. The bank had to borrow $24 million for one day to
cover the overdraft. The interest on this one-day loan cost the bank about
$5 million.

-- 
Mark Kelly
Manager of ICT, Reporting, IT Learning Area
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: +613 8520 9085, Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au
VCE IT Lecture Notes: http://vceit.com
Moderator: IT Applications Edulist <http://www.edulists.com.au/>

Want a good time? Call 0112358. Ask for Mr Fibonacci.
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