2. Software EngineeringFailures
ASIET Kalady
Major engineering failures due to software related course
Year 1900bug
Leap year bug
Interface Misuse
Security
Late and over budget
On time delivery
Unnecessarycomplexity
Year 1900Bug
o The year 1900 problem concerns the misinterpretation of years recorded by only their
last two digits, and whether they occurred before or after the year 1900. Unlike the year
2000 problem, it is not tied to computer software alone, since the problem existed before
electronic computers did and has also cropped up in manual systems.
o The most common issue raised by the year 1900 problem regards people's ages. Often, a
person's birth year was registered with only two digits, on the assumption that either it
was not important exactly how old a person is, or that no one lives longer than one
hundred years.
For example:
o In 1992, Mary from Winona, Minnesota received an invitation to attend a kindergarten.
Mary was 104 at that time.
o In several countries, especially in Europe, a national identification number was
introduced (often in the 1950s), including two-digit information about the birth year.
o The largest unwelcome side effect from this is people 100 or more years old being
mistaken for young children or in some cases, young children being mistaken for adults
3. Software EngineeringFailures
ASIET Kalady
Leap Year Bug
o Leap year bug ( Leap year problem) is a problem for both digital (computer-related)
and non-digital documentation and data storage situations which results from the wrong
calculation of which years are leap years.
o A supermarket was fined $1000 for having meat around 1 day too long on February 29,
1988.
o The computer program that printing the expiration date on the meat labels did not take
into account that 1988 was a leap year.
There are several types of leap year bugs.
o In 2012, Gmail's chat history showed a date of 12/31/69 for all chats saved on Feb 29,
2012. On the same day Microsoft's cloud computing solution Azure went down for 8
hours caused by a leap year bug.
o Some digital systems have wrongly calculated which years are leap years. The best-
known case occurred in Sony's PlayStation 3: The system treated 2010 as a leap year, so
a non-existent date February 29, 2010 was shown on March 1, 2010, and caused program
error.
o Microsoft Excel has, since its earliest versions, incorrectly considered 1900 to be a leap
year, and therefore that February 29, 1900 comes between February 28 and March 1 of
that year. The bug originated from Lotus 1-2-3, and was purposely implemented in Excel
for the purpose of backward compatibility.
o A leading multinational corporation’s cloud computing service outage, which affected
Governments and consumers, was caused by the additional day in February this year.
o The same leap year date bug also affected an Australian payment system used by the
health industry, resulting in 150,000 customers being prevented from using private health
care cards for medical transactions for two days.
4. Software EngineeringFailures
ASIET Kalady
Interface Misuse
o Interface Misuse is a type of interface error.
o A calling component call another component and makes an error in its use of
its interface
Eg: Parameters in wrong order.
o Misuse of interface, These are faults arising from a misunderstanding of the
required interface among separate units.
o On April 10, 1990, in London, an underground train left the station without
its driver.
o The driver had trapped the button that started the train, relying on the system
that prevented the train from moving when doors were open.
o The train operatorhad left his train to close a doorwhich was stuck.
o When the doorwas finally shut, the train simply left.
Security
o Security failure can arise from any aspect of the operations. Incidents might be man-made
or natural in origin.
o It is impossible to prevent all security failure, but focussing on the key risk mitigation,
management and prevention (deterrence) for certain risks will help maintain a cost-
effective and pragmatic security risk management approach.
o The cost of security will be outweighed many times by the cost of security failure which
may lead to business-critical exposure.
5. Software EngineeringFailures
ASIET Kalady
o CERT (Computer Emergency Response Team) at the software Engineering Institute is a
government-funded organization for assisting the community in dealing with security
incidents, vulnerabilities, and security know-how.
o The number of security incidents reported to CERT from the United States increased
from 252 incidents I 1900 to 21,756 in 2000 and more than 40,000 incidents were
reported in 2001.
Late and over budget
o In 1995, bugs in the automated luggage system of the new Denver
International Airport caused suitcases to be chewed up. The airport opened
16 months late. $3.2 billion over budget, with a mostly manual luggage
system.
o In 2002, the Swanick Air Traffic Control system covers all the enroute air
traffic over England and Wales.
o The system was delivered substantially over budget (cost £623 million,
originally planned at £350 million) and 6 years late. Two major upgrades of
the system were delivered after training of the traffic controllers had started.
On time delivery
o Attaining acceptable delivery performance is the most significant manufacturing
challenge faced by many organizations.
o ƒ Metrics of excellence in customer service are on-time pickup and on-time delivery.
o Success or failure results with or beyond the carrier’s control Success or failure occurs
from the synergy of several SNI actions.
o These service metrics occur in the context of other operational measures budgetary
targets utilization of driver associates equipment availability safety requirements
6. Software EngineeringFailures
ASIET Kalady
o After 18 months of development, a $200-million system was delivered to a health
insurance company in Wisconsin in 1984.
o However, the system did not work correctly: $60 million in overpayments were issued.
The system took 3 years to fix.
Unnecessarycomplexity
o The C-17 cargo plane by McDonnell Douglas ran $500 million over budget
because of problems with its avionics software.
o The C-17 included 19 onboard computers, 80 microprocessors, and 6 different
programming languages.
o Each of these failures resulted from a software related problem. In some
cases, developers did not anticipate seldom-occurring situations (a person
living more than 100 years, leap years impacting expiration dates).
o In other cases, developers did not anticipate the user actively misusing the
system (tapping down a button, exploiting security holes I network software).
o In yet other cases, system failures resulted from management failures (late
and over budget delivery, on time delivery of an incorrect system,
unnecessary complexity).
