- Week of 8 March (evening exam)
- Week of 9 April (in class)
- Final: Tuesday, 7 May, 10:30AM (scheduled final period)

**Note about the Practicum 2 writeup**. For phase 4 I want the pseudo-code for the recursive function, not for phase 4.-
**Practicum 2:**what is "%fs:0x28"? This is a reference to the way that the intel machine language adresses memory, something that we have not (and will not) talk about in class. If you're interested, see this article: X86 memory organization. You can safely ignore this instruction when you see it, but the larger lesson is that you have to deal with some uncertainty when working with the bomb. You won't know everything, but you have to use what you do know to figure out what is happening. -
**Lab 7:**why is the instruction "sar 0x3f, %rdx" there? -
**Problem set 2:**it's ok to use the time.h library to convert seconds into a date formate. Check out the strftime function in particular.

Integer division always rounds it’s result by rounding towards 0. So if we do 5 the result is 2.5 which is rounded to 2. This is the same result that we get if we shift 0101 to the right one position, i.e., 0010. If we do −5, however, the 3 result is −2.5 which should round toward 0, i.e., to −2. The 2’s complement version of −5 however is 1011. If we shift it right we get 1101 or −3 not −2. To fix this, we can add one before we shift, i.e., −5 + 1 = −4 or 1100. When we shift this right we get 1110 or −2, the correct answer. How can we do this without an if statement to test whether the number is positive or negative? If a 2’s complement number is positive, the sign bit is 0. If the 2’s complement number is negative it’s sign bit is 1. So we shift the sign bit all the way to bit position 0 (63 bits if we have a 64 bit number). If the number is negative, it results in the value ”1”; if the number if positive it results in the value ”0”. We then add this to the number that we are to divide, i.e., we add ”1” to a negative number and ”0” to a positive number. Then when we shift right, the number will be rounded in the correct way.

Problem Set 2 is now due on
Friday, 1 February **Monday, 11 Feb** at the beginning of class.

** Thursday, 23 January,** read the Unix tutorial Intro, tutorial 1, tutorial 2.
**No** quiz on **Monday, 28 January**

Problem Set 1 is due on Monday, 28 Jan at the beginning of class.

- AMD is back!
- Linux vulnerability was found that uses heap spraying to exploit the kernel. This technique relies on a knowledge of the runtime stack and the heap, both of which we'll be looking at later this semester.
- Speaking of programming vulnerabilities, check out the SAN Institute's list of the 25 most dangerous software errors.
- Buffer Overflow in the news!!

- Interested in what happened to the engineers from
*Soul of a New Machine*? Check out this article from*Wired*magazine in 2001. And this page has a photo of the development group in 1980. - vi or emacs? See this article.
- Describe computer science in 5 words:
BI **Bits in real life**. Ariane 5, 1996. See here