Notes BB-1

CPSC 110-08: Computing with Mobile Phones

Reading: Blown to Bits, Chapter 1

Digital Explosion: Why Is It Happening and What Is at Stake?

Principles addressed: Key Concept IIA. A combination of abstractions built upon binary sequences can be used to represent all digital data. Learning Objective IIA5: The student can describe the combination of abstractions used to represent data. [P3] Learning Objective IIA6: The student can explain how binary sequences are used to represent digital data. [P5] Big Idea VII. Impact: Computing has global impacts. Key Concept VIIA. Computing affects communication, interaction, and cognition. Key Concept VIIB. Computing enables innovation in nearly every field. Key Concept VIIC. Computing has both beneficial and harmful effects. Key Concept VIID. Computing is situated within economic, social, and cultural contexts. Corresponding Lecture Ideas: * Bits and Bytes - Representing numbers with bits - Representing letters with bits (ASCII) - Same bit string can represent either a number or a letter or part of an image * Moorse Law and exponential growth - Graph of Moore's law; question what is the limit ? - Exponential growth in computing power - Exponential growth in data and information - Limits on computation

Bits as the Natural Unit of Information

This was the seminal insight of Claude Shannon, founder of information and communication theory. As this chapter illustrates all information stored on computers (documents, photos, songs, etc.) and communicated through the Internet (email, blogs, twitter posts, etc.) are represented as bits, zeros and ones.

Digital data are represented in discrete bits. Analog data are represented as a continuous quantity. Think of the difference between a digital watch that displays hours, minutes, seconds, and tenths of a second, and an analog clock, with hour hand, minute hand, and a sweep second hand.

Think of the difference in fidelity between digital vs. analog recordings.

Moore's Law

Moore's law is the observation that the number of transistors that could be packed onto a integrated circuit seemed to double ever two years or so. This remarkable trend about exponential growth in chip density has proved to be true for 40 years now.

Someone offers you a summer job and offers you two payment schemes: (1) $10 per hour for 40 hours per week for 30 days or (2) One cent on day 1, two cents and day two, four cents on day three and on (doubling each day) for 30 days. Which play would you choose? Click here to see how exponential growth affects this question.

It's All Just Bits

Binary digits (bits) correspond naturally to electronic circuits where 1 represents 'on' and 0 represents 'off'.

The same string of bits can represent different types of information depending on the context.

0100 0001 could represent the binary numeral for the decimal value 65
0100 0001 could represent the ASCII letter 'A'
0100 0001 could represent the amount of the color Red in the RGB color model.
0100 0001 could represent the MOV B,C machine operation on the Intel 8080 8-bit processor

Data Abstraction: How RGB Colors Are Represented in Bits

The RGB model adds together 3 primary colors, Red, Green, and Blue.

Each primary color component (R,G,B) can be represented as an 8-bit byte. Historially an 8-bit byte was used to represent a single character in computer memory and it therefore become the most basic addressable element in computer memory.

Eight bits can represent 256 (2⁸) numbers ranging from 0 to 255.
More generally:
1 bit can represent 2 (2¹) alternatives: 0 or 1.
2 bits can represent 4 (2²) alternatives: 00, 01, 10, 11
3 bits can represent 8 (2³) alternatives: 000, 001, 010, 011, 100, 101, 110, 111
4 bits can represent how many alternatives? Can you list them?

A color can be represented as a triplet of three integers (r,g,b) specifying the amount of each color to be added together.

If there are 256 possible values for each of R,G,B, the triplet can represent 256 × 256 × 256 = 16,777,216 different colors, which is corresponds well to the number of colors the human eye can distinguish.

(65,65,65) = Grey
(255,0,0) = Red
(0,255,0) = Green
(0,0,255) = Blue
(65,0,0) = Brown

Try to mix your own colors: Colorschemer.com

Perfection is Normal

Because they are based on strings of discrete bits, digital copies (as opposed to analog) are perfect copies.
Computer scientists and engineers have developed effective error detection and error correction schemes to insure accurate data representation and communication.
Example: Parity Bit Scheme. For each 8-bit byte, 7 bits are used to represent the data. In and even parity scheme the eighth bit, the parity bit, is set to 1 if the number of 1s in the data (7-bits) is odd, thereby making the number of 1s in the 8-bit byte even. It is set to 0 if the number of 1s is even.

Q: What would happen in this scheme if the value of 2 bits were switched?

Want in the Midst of Plenty

Data storage devices change. Data stored on floppy disks (in my office) are no longer easily retrievable.

Nothing Goes Away

Today massive amounts of data (and data about us) are stored on databases in multiple copies. These data will never go away. Computer scientists are working hard to develop data mining algorithms to retrieve and analzye these data. Think of the law enforcement and privacy implications.
Example: NPR Story on Mobile Face Recognition App

Bits Move Faster Than Thought

The Internet connects the entire world instantaneously. This has implications for how business is done (outsourcing) to how skin cancer is diagnosed (an Android app ).

Technology is Neither Good nor Bad
Technology Brings Risks and Opportunities

Give an example of how the digital explosion is "neither good nor bad" but has both positive and negative implicaitons.

CPSC 110-08: Computing with Mobile Phones Reading: Blown to Bits, Chapter 1