- Writing a shell;
	- Kernel hacking;
	- File system code; and
	- Networking code.

	- Scheduling; and
	- Virtual memory.

	Think of a system as a large (or maybe small) set of individual pieces, working together.
	Outside of the system is the environment that it runs in.
	The system has a membrane, or skin, separating it from its environment. 
		This is called its interface.
	For a person also within the environment, the system cannot be seen; 
		only the interface can been seen and interacted with.

	Economies of Scale would be a good example of incommensurate scaling:
	The cost per unit of an item grows down as the system grows.
	In Adam Smith's scenario, there are a village of self-sufficient people.
	If any one of the villages desired a pin, they would have to cut a wire and sharpen it manually each time.
	It would be much "cheaper" to have one villager (a blacksmith) that mass produces pins for all of the villagers.
	Unfortunately, the downside to this scenario is that it can cause waste if too many pins are created.
	
	Diseconomies of Scale is another example:
	The cost per unit of an item grows up, not down, as the system grows.
	An example of this would be a star network.
	The downside to this idea is that it can cause breakage.

	The Tacoma Narrows Bridge disaster is an example of an emergent property
		manifesting itself with increases in scale.
	The bridge was built to the most advanced engineering specifications of the day.
	However, the designers did not account for the resonance effects of multiple gusts of wind,
		blowing against the bridge, one after the other.
	These effects were negligible in the smaller prototypes of the bridge, but they had to be
		accounted for in the full-sized version.
		
	Operating systems, of course, are much more complicated than bridges...
	Plus, the OS attackers have "wind generators" ;-) .
	
	A significant episode of emergent properties occurred right here at UCLA!
	The internet access newly made available for students in the dorms (this was around the year 2000),
		became quickly overrun with music pirating using Napster!

	A number of years ago, Microsoft endeavored to create a file system that accepted Japanese characters as filenames.
	Their first attempt failed--due to the Shift JIS character encoding used on Japanese computers.
	This encoding used two bytes to represent characters. Each byte, individually, appeared very similar to an
		ASCII character, except that the most significant bit in the first byte was a 1.
	Ex of Shift JIS: 11001010 | 01011001 . The most significant bit is a 1. This denotes a Japanese character.
	
	However, Microsoft Windows only recognized the second byte (which has a leading zero like ASCII). This led
		to Japanese files and directories being mis-named and lost on the system!
	This led to Microsoft's switch to UTF-8 character encoding, which is still used today. This compromise leads
		to the next problem area in OS design,

	UTF-8 requires 3 bytes instead of 2, which makes it slightly more expensive.
	Filenames take up more disk space when UTF-8 encoding is used.
	But it's necessary to ensure that filenames in Windows written in other languages are interpreted
	correctly by the OS.

	Another example exists in the realm of security: the use of 2-factor authentication.
	This can occur by requiring both a password as well as a key fob (providing RSA encryption), rather than relying solely on passwords.
	But what if a user's key fob gets lost? Or... it gets programmed wrong!? Or..... the batteries fail!?!?!
	This is yet another tradeoff! Extra security vs. the risk of something going wrong with the key fob.