10 greatest computer bugs of all time.

10. Mariner 1 Venus probe loses its way: 1962
A probe launched from Cape Canaveral was set to go to Venus. After
takeoff, the unmanned rocket carrying the probe went off course,
and
NASA had to blow up the rocket to avoid endangering lives on earth.
NASA later attributed the error to a faulty line of Fortran code.
The
report stated, "Somehow a hyphen had been dropped from the guidance
program loaded aboard the computer, allowing the flawed signals to
command the rocket to veer left and nose down...Suffice it to say,
the
first U.S. attempt at interplanetary flight failed for want of a
hyphen." The vehicle cost more than $80 million, prompting Arthur
C.
Clarke to refer to the mission as "the most expensive hyphen in
history."

9. Radiation machine kills four: 1985 to 1987
Faulty software in a Therac-25 radiation-treatment machine made by
Atomic Energy of Canada Limited (AECL) resulted in several cancer
patients receiving lethal overdoses of radiation. Four patients
died.
When their families sued, all the cases were settled out of court.
A
later investigation by independent scientists Nancy Leveson and
Clark
Turner found that accidents occurred even after AECL thought it had
fixed particular bugs. "A lesson to be learned from the Therac-25
story is that focusing on particular software bugs is not the way
to
make a safe system," they wrote in their report. "The basic
mistakes
here involved poor software-engineering practices and building a
machine that relies on the software for safe operation."

8. AT&T long distance service fails: 1990
Switching errors in AT&T's call-handling computers caused the
company's long-distance network to go down for nine hours, the
worst
of several telephone outages in the history of the system. The
meltdown affected thousands of services and was eventually traced
to a
single faulty line of code.

7. Patriot missile misses: 1991
The U.S. Patriot missile's battery successfully headed off many
Iraqi
Scuds during the Gulf War. But the system also failed to track
several
incoming Scud missiles, including one that killed 28 U.S. soldiers
in
a barracks in Dhahran, Saudi Arabia. The problem stemmed from a
software error that put the tracking system off by 0.34 of a
second.
As Ivars Peterson states in Fatal Defect, the system was originally
supposed to be operated for only 14 hours at a time. In the Dhahran
attack, the missile battery had been on for 100 hours. This meant
that
the errors in the system's clock accumulated to the point that the
tracking system no longer functioned. The military had in fact
already
found the problem but hadn't sent the fix in time to prevent the
barracks explosion.

6. Pentium chip fails math test: 1994
The concept of bugs entered the mainstream when Professor Thomas
Nicely at Lynchburg College in Virginia discovered that the Pentium
chip gave incorrect answers to certain complex equations. In fact,
the
bug occurred rarely and affected only a tiny percentage of Intel's
customers. The real problem was the nonchalant way Intel reacted.
"Because we had been marketing the Pentium brand heavily, there was
a
bigger brand awareness," says Richard Dracott, Intel director of
marketing. "We didn't realize how many people would know about it,
and
some people were outraged when we said it was no big deal." Intel
eventually offered to replace the affected chips, which Dracott
says
cost the company $450 million. To prove that it had learned from
its
mistake, Intel then started publishing a list of known "errata," or
bugs, for all of its chips.

5. Intuit's MacInTax leaks financial secrets: 1995
Intuit's tax software for Windows and Macintosh has suffered a
series
of bugs, including several that prompted the company to pledge to
pay
any resulting penalties and interest. The scariest bug was
discovered
in March 1995: the code included in a MacInTax debug file allowed
Unix
users to log in to Intuit's master computer, where all MacInTax
returns were stored. From there, the user could modify or delete
returns. Intuit later ended up winning BugNet's annual bug-fix
award
in 1996 by responding to bugs faster than any other major vendor.

4. New Denver airport misses its opening: 1995
The Denver International Airport was intended to be a
state-of-the-art
airport, with a complex, computerized baggage-handling system and
5,300 miles of fiber-optic cabling. Unfortunately, bugs in the
baggage
system caused suitcases to be chewed up and drove automated baggage
carts into walls. The airport eventually opened 16 months late,
$3.2
billion over budget, and with a mainly manual baggage system.

3. Java opens security holes; browsers simply crash: 1996 to 1997
All right, this is not a single bug but a veritable bug collection.
We
include this entry because the sheer quantity of press coverage
about
bugs in Sun's Java and the two major browsers has had a profound
affect on how the average consumer perceives the Internet. The
conglomeration of headlines probably set back the e-commerce
industry
by five years.
Java's problems surfaced in 1996, when research at the University
of
Washington and Princeton began to uncover a series of security
holes
in Java that could, theoretically, allow hackers to download
personal
information from someone's home PC. To date, no one has reported a
real case of a hacker exploiting the flaw, but knowing that the
possibility existed prompted several companies to instruct
employees
to disable Java in their browsers.
Meanwhile, Netscape and Microsoft began battling in earnest in the
much-publicized browser wars. That competition inspired both
companies
to accelerate the schedules for their 4.0 releases, and the result
has
been a swarm of bugs, ranging from JavaScript flaws in Netscape's
Communicator to a reboot bug in Microsoft's Internet Explorer.
Communicator is now in Version 4.04 for Windows 95 and Windows NT,
six
months after its first release. Internet Explorer 4.01, the first
of
presumably many bug-fix versions, arrived in December, two months
after the initial release of IE 4.0.

2. Deregulation of California utilities has to wait: 1998
Two new electrical power agencies charged with deregulating the
California power industry have postponed their plans by at least
three
months. The delay will let them debug the software that runs the
new
power grid. Consumers and businesses were supposed to be able to
choose from some 200 power suppliers as of January 1, 1998, but
time
ran out for properly testing the communications system that links
the
two new agencies with the power companies. The project was
postponed
after a seven-day simulation of the new system revealed serious
problems. The delay may cost as much as $90 million--much of which
may
eventually be footed by ratepayers, and which may cause some of the
new power suppliers to go into debt or out of business before they
even start.

1. The millennium bug: 2000
For a long time, programmers have saved memory space by leaving
only
two numeric fields for the year instead of four: 87 instead of
1987,
for example. When clocks strike midnight on January 1, 2000, this
programming shorthand will make millions of computers worldwide
think
it's 1900, if their software isn't fixed before then. The so-called
year 2000 (Y2K) bug has given birth to a cottage industry of
consultants and programming tools dedicated to making sure the
modern
world doesn't come to a screeching halt on the first day of the
next
century. Some say that the bug will cause airplanes to fall from
the
sky, ATMs to shut down, and Social Security checks to bounce. At
the
very least, the bug is a huge and expensive logistical problem,
although most vital organizations now say they will have fixed the
critical portions of their systems in time.