CS111 Lecture 1
Illicit Coding Schemes
Imagine a virtual server running atop a real server. This real system has a file system.
It is running several virtual servers. There are subdirectories for each virtual server.
You can tar attack another vm running on the same server as you by using symbolic links and backups.
DNS poisoning: When a DNS lookup occurs, time a planned response that sends the wrong IP address
Terms
System- group of components working together with connections working between them.
Oxford English Dictionary Version:
I. An organized or connected group of objects.
II. A set of principles, etc., a scheme, method.
Etymology: Greek.
Systima written in greek: organized whole; government; constitution; a body of people or animals; musical “something”; group of connected verses in a poem.
Operating System according to the American Heritage Dictionary:
Software designed to control the hardware of a specific data processing system in order to allow users and application programs to make use of it.
He does not like this definition
Encorta version:
A master control program of a computer.
Wikipedia v. 602065231 at March 31, 2014:
A collection of software that manages computer hardware resources and provides common services for computer programs.
18 Lectues 1 midterm 1 final (open book and notes)
midterm is 100 mintes, final is 180 minutes.
Total grade: midterm is 1/9 and the final is 2/9 of the grade.
Homework: 4 labs (teams of 2) (e.g. pair programming, which means one sits at the laptop while the other person thinks strategically.) 1/12 each so that eventually comes out to 1/3 in total
The rest of the course is 2 minilabs (solo) 1/15 each
Then a design problem where you pick a lab and do extra work with it (teams of 2) each lab will suggest its own design problem but you can pick your own as well. 1/12 comes with a written report
One scribe notes, about the lectures (in HTML 4.0 or 5) Validated. 1/20 up to 4 can collaborate.
Last week of class 2-3 page pseudo research paper where you summarize work done in a recent field of operating systems. 1/15
Lateness policy: 2^(n-1) % policy where n is the number of days late.
Due dates on syllabus which is on the website
Scribe Notes: due one week after lecture due at 23:59:59
Nothing can be submitted after June 6.
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Problems and computer systems
Waterbed effect
You push down on one side of the bed and the other side will inflate up. This means that when you are trying to improve some part of the system, often times other parts of the system will get slightly worse.
Example: sort a big array. Lets say that each byte is 1 KiB and you have 1GB of array.
#####Ex. Sorting a big array#####
- 1 KiB -> 2^20 entries, 1^20 sized blocks of data
- Qsort (1<<20, 1<<10, cmp)
- Faster: integers (4 byte), initialize to itself, qsort index (1<<20, sizeof(int), cmp))
- Assuming Qsort is NlogN -> array of indexes vs. array of data
- + copying overhead reduced by a factor of 256
- - 0.5% more memory
- - more complicated, more lines of code, more bugs possible
- - cmp slower than cmp (this could make or break sort)
- Ex: if original blocks are only 2 bytes instead of 1^10n
- - later accesses are not sequential
####Incommensurate Scaling####
- Not verything scales at the same rate
(Economies of scale, Adam Smith)
- Should all workers make pins or just one get really good?
- As pin factory grows, get **way** better at pins
- + quality increases with scale
- - can cause waster
#####Diseconomies of Scale#####
- **Ex.** 100 based t switch(link to t switch)
- all ports in switch connected by big box
- Less than eight in switch == cheap!
- 100 in switch == Holy vestuvius Batman!
- 1000? Forget about it
**Reason:** Connecting box just does not scale, processing in parallel too expensive, processing seq. just not fast enough
**Recall CS 33**
####Propagation of Effects####
System split nicely into modules with APIs + small change to one module -> another module breaks
- Chain reaction of small effects (propagtion of effects)