Quiz submission record for quiz3-2-1 at Wed Jul  7 09:49:21 2004:

Your Answer for Question 1:
A possible way to exploit a security hole is by using overflow.  Computers must be certain to check for overflow/underflow when doing math; if someone were able to cause overflows in computer operations it could completely alter the performance - especially since data is often in the form of numbers (be them integers, floats, etc).  One possible (though horribly unreasonable) technique to prevent this would be to disallow negative numbers; of course, the terrible tradeoff would be disallowing negative numbers (hehe), which would also severely limit the power and range of uses of a computer. 

Your Answer for Question 2:
A "subnormal" (aka a denormal number) is a number with the same exponent as zero but a nonzero significand. They are used to try and get more precision from a floating-point operation, but also provide problems for programmers who may or may not expect subnormals in their programs. (and who otherwise must handle subnormals gracefully!) Subnormals also allow for "gradual underflow" - that is, they allow a number to degrade in significance until it becomes 0.  In fact, the smallest single precision denormalized number is a power of 2^-23 times smaller than the smallest single precision normalized number.

Your Answer for Question 3:
Many programmers wrote (0.5 - x) + 0.5 because they had to compensate for the lack of a guard digit.  In other words, "in the old days" hardware lacked a guard bit (bits on right during intermediate calculations - if every intermediate result truncated to the exact number of digits, there would otherwise be no opportunity to round the final answer) in double precision.

Your Answer for Question 4:
FOR: standards are widely implemented, require minimum accuracy, operations must be commutative, has fixed a lot of problems from the past (esp. around floating points), history proves that it is very difficult and time consuming to create an alternative

AGAINST: need to represent "the compiler-writing community" more so that more hardware features are available to programmers - primarily, IEEE 754 and its followers would benefit greatly from compiler support since otherwise great features are worthless.


Your unique submission ID is quiz3-2-1-cs61c-ax-1089218961-2417.