Unit 1 Com Sci Assessment

example of abstraction (something where you don't completely understand how it works but can use it w/ confidence)

planes, cars, tv, etc

Computer scientists like to...

start counting at 0!

Abstraction

Representing text is an example of abstraction, which is when we create simplified representations of something more complex.

ASCII (American Standard Code for Information Interchange)

a widely used system for character encoding.

the smallest piece of information a computer can store

bit

Each place value represents one 'bit' (binary digit)

bit can be 0 or 1

black pixel = ? , white pixel = ? ( 1 bit per pixel )

black pixel = 0, white pixel = 1

Lossy Compression

A process for reducing the number of bits needed to represent something in which some information is lost or thrown away. This process is not reversible.

Lossless Compression

A process for reducing the number of bits needed to represent something without losing any information. This process is reversible.

1 place value =

2 possible patterns

byte

8 bits long

2 place values =

4 possible patterns

How many patterns (made up of 2 shapes) can you make with 3 place values?

8

How would you explain a number system to someone who had never seen numbers before?

A number system is a system that uses a combination of shapes to express information. For example, there is the binary number system that expresses information with a combination '1' and '0', and there is the decimal number system that expresses information with the combination of '0', '1', '2', '3', '4', '5', '6', '7', '8', and '9'.

Sampling

A process for creating a digital representation of analog data by measuring the analog data at regular intervals called samples.

intellectual property

A product of the intellect, such as an expressed idea or concept (music, images, videos, etc, etc)

Digital Data

Data that changes discreetly through a finite set of possible values

Analog data

Data with values that change continuously, or smoothly, over time. Some examples of analog data include music, colors of a painting, or position of a sprinter during a race.

Which of the following would result in a better digital approximation of an analog black and white image?

Decreasing the size of each sample square, thus increasing the number of samples taken.

An author is preparing to send their book to a publisher as an email attachment. The file on their computer is 1000 bytes. When they attach the file to their email, it shows as 750 bytes. The author gets very upset because they are concerned that part of their book has been deleted by the email address. If you could talk to this author, how would you explain what is happening to their book?

Don't worry! What you are witnessing is a lossless compression. This essentially means that the computer is taking shortcuts to reduce the size of the data. Data in a lossless compression can always be decompressed and reconstructed to its original form. So how is the data in your book compressed? Words and phrases that are repeated often are compressed. For instance, if the word 'the' appears 5,000 times in the book, it may be expressed as 'the x 5,000' as opposed to being stored 5,000 different times. The publisher will receive your book intact!

Each time we add another bit, what happens to the amount of numbers we can make?

Each time another bit is added, the amount of numbers we can make doubles. (Unlike in decimal, when another place value is added the number of numbers we can make x10)

Creative Commons (some rights reserved)

Free, easy-to-use copyright licenses provide a simple, standardized way to give the public permission to share and use your creative work on conditions of your choice

layers of abstraction in color images

Look @ ss

When using bits to represent fractions of a number, can you create all possible fractions? Why or why not?

No, it is impossible to represent all possible fractions with bits. This is because there is a limited number of fractions that can be represented with the available number of place values. Something called a "roundoff error" occurs when an exact value cannot be expressed with the place values available.

Which statement about analog and digital images is true?

Sampling an analog image more frequently produces a digital image with a better representation.

Describe how the process of sampling, RGB pixels, and binary sequences work together to display a digital color image.

Sampling works to recreate the 'framework' of analog images by measuring the analog data at regular intervals and assigning these samples to pixels. Color is then added to the framework of the image with the cooperation of binary sequences and RGB pixels. The greater the number of bits for each RGB pixel, the more the levels of red, green, and blue light may be altered. These binary sequences represent a vast range of colors and hues in the digital image.

How many bits would be needed to count all of the students in class today?

Six bits would be needed to account for 32 students in class. 10 0000

Many museums have digital catalogs of their collections. What are the potential benefits and harms of creating these digital catalogs?

Some potential benefits of digital catalogs are that they are easily accessible, can be viewed from virtually anywhere, and can be updated frequently. The biggest harm of creating a digital catalog is the lack of security. People who want to steal the museum's data can do so more easily, and it is more likely that someone would attempt to steal data.

You've been given a new cell phone with a 2 gigabyte data plan. You plan to use your phone for text messages, images, video, and music. Which of these categories are best compressed using lossless compression? Which of these categories are best compressed using lossy compression? Why?

Text messages are best compressed using lossy compression. Whether they realize it or not, many people use lossy compression when they are texting already. Certain abbreviations have been popularized to communicate common phrases. For example, 'ttyl' stands for 'talk to you later'. Though abbreviations use less data, they are just as effective at communicating as a message that's written out. Videos, images, and music on the other hand, are best compressed using lossless compression. When the audio or image quality is worsened, the content is less enjoyable for the consumer.

Binary

The binary numbers system is base-2. There are two different symbols used to represent numbers (0-1).

"The binary pattern 01000001 represents the number 65." Write a brief response explaining whether you believe this statement is always true. Explain your reasoning.

The binary pattern '01000001' does not always represent the number 65. While this representation can represent '65' in the decimal system, it can also represent 'A' in ASCII. The meaning behind the pattern depends on context and what system the pattern is being corresponded with.

What are the similarities and differences between the binary and decimal systems?

The binary system is base-2 while the decimal system is base-10. Computers use binary due to the simplicity of the two-option (these two options are equated to on v. off) system, and people typically use the decimal system. Despite these differences, the two systems share some similarities. Both are systems of shapes and both have a one's place. Lastly, when there are zeros on the left-hand side of either a binary or decimal number, the value is unaffected.

Assume your friend just sent you 32 bits of pixel data (just the 0s and 1s for black and white pixels) that were encoded after sampling an image. Choose the two statements that are true.

The correct width and height must be input into the pixelation widget to produce the image. The fact that only 32 bits were used to represent the image indicates relatively large sample squares were used. The digital image may vary from the analog image significantly. x The digital image would be an exact copy of the analog image. x The 32 bits of pixel data is enough to produce the image using the widget. Nothing else is needed. ( REQUIRES THE FIRST 16 bits for dimensions -- width by height )

What is the most important quality of lossless compression?

The data is transformed to usually make it smaller. It can always be re-constructed back to the original.

Decimal number system

The decimal number system is base-10. There are ten different symbols used to represent numbers (0-9)

Modern car odometers can record up to a million miles driven. What happens to the odometer reading when a car drives beyond its maximum reading?

The odometer experiences an overflow error when a car drives beyond its maximum reading. The odometer is unable to express more than a million miles.

Imagine you were using some of our pixelation tools to create an image and you posted it online for your friends to see - but, a week later you find out someone took that image and put it on a T-shirt that they're selling for $10 each. Now that we understand Copyright, what would need to change in order for the scenario from the warm-up to be okay?

This scenario would be okay if the image had a Creative Commons license applied to it. More specifically, the license would have to allow others to use the image for commercial use.

How is a Creative Commons license different from a regular copyright?

Under a regular copyright, all rights of the creative work are reserved to the original owner. This protects the work from being used by people and in ways the creator doesn't consent to. A Creative Commons license on the other hand, is applied to a copyright so others can benefit from the work. The license outlines how others can use the content and under it, only some rights are reserved to the original owner. Is the content allowed for commercial use? Can the content be modified? These are some questions answered by the Creative Commons license.

Compression

Using abbreviations and symbols is a form of compression, where we try to represent the same information with fewer characters

Your computer science teacher asks you to sample a black and white image that is 4" x 6". How would you sample the image to provide a good digital approximation using the pixelation widget? What sample size would you use? How would your decision affect the digital representation?

Using the Apple logo I created for reference, I know that a sample size of 15 by 15 would do a decent job of representing an image with dimensions of 2" by 2". Thus, I would sketch the 4" by 6" image on a grid of 20 by 25. I would use 500 sample squares. The large number of sample squares would allow for a well-defined and accurate digital approximation.

Overflow error

error from attempting to represent a number that is too large.

Prototype

is a fancy word that means a preliminary sketch of an idea or model for something new. It's the original drawing from which something real might be built or created.

roundoff error

occurs when an exact value cannot be made with available place values. Value is too precise.

Copyright ( all rights reserved )

the exclusive legal right, given to an originator or an assignee to print, publish, perform, film, or record literary, artistic, or musical material, and to authorize others to do the same.