Marisa Cheng

9/24/09

How Computers Work

Assignment 2

Contributed with: Valeria Vega

[Highlights by Joe.]

1. When A is 0, B is 1, and C is 0, the output is 0.

When A is 1, B is 0, and C is 1, the output is 1.

When A is 1, B is 1, and C is 1, the output is 1.

The pattern is that when there are two or more “1”s in the input, then the lights light up.

According to Wikipedia, “The AND gate is a digital logic gate that implements logical conjunction. A HIGH output (1) results only if both the inputs to the AND gate are HIGH (1). If neither or only one input to the AND gate is HIGH, a LOW output results. In another sense, the function of AND effectively finds the minimum between two binary digits.” On the other hand, “The OR gate is a digital logic gate that implements logical disjunction. A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). If neither input is HIGH, a LOW output (0) results. In another sense, the function of OR effectively finds the maximum between two binary digits.” According to Prof. O’Rourke’s Notes 4, the AND chart is obtained by “inputting A as 0, and b as 0 is 0; A as 0 and b as 1 is 0; A as 1 and B as 0 is 0; and A as 1 and B as 1 is 1.” The “1” represents “shut closed” and the “0” represents “leave open.” On the other hand, the OR chart is obtained by “inputting A as 0, and b as 0 is 0; A as 0 and b as 1 is 0; A as 1 and B as 0 is 1; and A as 1 and B as 1 is 1.”

Site: Professor O’Rourke’s Notes 4: http://maven.smith.edu/~orourke/103/restricted/Notes4.html

Wikipedia “AND Gate” http://en.wikipedia.org/wiki/AND_gate

Wikipedia “OR Gate” http://en.wikipedia.org/wiki/Or_gate

2. [No need to criss-cross the wires---works either way.--JOR]

3. If the Library of Congress were digitized, it would use at least “20 terabytes of information.” If other information were considered, “this [information] is misleading because the Library contains many items in addition to books, such as manuscripts, photographs, maps, and sound recordings, that, if digitized, would amount to much more information.” If there were 2TB disks available, one would need at least 10 disks to hold the entire Library of Congress.

Site: Wikipedia “Library of Congress”

http://en.wikipedia.org/wiki/Library_of_Congress

4. The “world’s largest flash drive is a 256GB drive from Kingston.”

Site: Google “What is the world’s largest USB drive?”

http://allthingsusb.com/content/What-is-the-worlds-largest-USB-flash-drive

5. The Amazon Kindle uses the “electronic ink” display so that it is easier to read and so the eyes do not become tired. This screen “looks more like paper” than a computer screen. It “reflects light” as “the same way that paper does.” There is also no “backlight” so one must use an “external light source.” Another aspect is that “electronic ink actually uses millions of microcapsules, only a few microns wide. Each microcapsule contains a clear fluid and thousands of white and black particles. The white particles carry a positive magnetic charge and the black particles have a negative charge.” The “positively and negatively charged particles” contribute to the “electronic ink displays.” The actions are that “When an electrode emits a negative charge, it repels the negatively-charged black balls, pushing them to the top of the microcapsule. At the same time, the charge attracts the positively-charged white particles to the bottom of the microcapsule. When the electrode emits a positive charge, the white and black particles switch places and the screen appears to be blank.” However, “if the electrode emits a positive charge, then it will attract the balls, pulling them down through the ink. The display then reveals the ink to the viewer. Working together, thousands of electrodes and millions of microcapsules generate the text and images you can see on an electronic ink display. Through precise charges the Kindle can display a range of grays to provide shading in images.” Also, the Amazon Kindle “uses less energy” than other “LCD” devices because “the Kindle pulls power from its battery only during the initial page generation” so it can last “for up to a week on a single charge.” In conclusion, the Amazon kindle is currently in black and white. But in the future, it might become a multi-colored Kindle.

Site: Google “How the amazon kindle works”

http://electronics.howstuffworks.com/gadgets/travel/amazon-kindle3.htm