Winter16 CS111 Lecture 1
Course logistics
Course Website
What is a system?
OED original (1928)
- An organized or connected group of objects
- A set of principles, etc, a scheme, method
- from Ancient Greek, σύστημα,
organized whole, government, constitution, a body of people or
animals, musical instruments.
Operating System
- American Heritage
- software designed to control the hardware of a data proccessing system in order to
allow users and applications programs to make use of if.
- Encarta (2007)
- master control program in a computer
- Wikipedia 698216816 (2016-01-04)
- collection of smaller programs and softwares that is used to control and operate the
computer system
Major Missing Issues of the Definitions above
- resource management
- reliability and error handling
- Security
Example:
Circa 2000 hardware
$ ls -l big
-rw-rw-r-- 1 eggert faculty 9223372036854775000 Oct 6 11:31 big
$ grep x big
$ time grep x big
real 0m0.009s
This gives us a speed of approximately 1022b/s. According to
http://what-if.xkcd.com/31/ the
bandwidth of the Internet is 1011b/s, and if we hire all the freight
trucks in the US to transport hardrives, the speed will be approximately 0.5Zb/s.
The explanation behind this amazingly high speed is because that in ZFS(zeta File System),
big is an intensional file, which only stores a description or program of the file on the
desk. This type of file can be used in anti-virus softwares to allievate the workload of
the program.
Problem Areas in OS Design
- Incommensurate Scaling
- not everything scales at the same rate
- economies of scale
- can cause waste
Example: O(logN) algorithm and Adam Smith's
Pin Factory
- diseconomies of scale
- can cause breakage
Example:O(logN2) algorithm
- Emergent Properties
- larger systems have properties that smaller prototypes didn't
Examples:
- Tacoma Narrows Bridges
- UCLA Campus Network
- Propagation of Effects
- Propagation of effects also exist in other systems, but in computer
systems, pathways for propagations are more effective.
Example:
Internationalization: Shift-JIS encoding used in Windows system
- Tradeoffs
- Waterbed Effect
Example:
- In previous example, Linux system chose UTF-8 encoding rather
than Shift-JIS encoding but UTF-8 encoding requires more memory
than Shift-JIS encoding does
- Security tradeoff: password VS RSA and password