3.10 Impacts of CS: Electronic Documents

3.10 Impacts of CS: Electronic Documents Curriculum Page

Short Answer Questions:

1. What is metadata? Give an example of how a piece of metadata could be used to increase the usefulness of an image or document.

• Metadata is data that is stored to provide information for other data. For example metadata for a document includes the name of the doc, owner of computer, data file creation date, edited versions, comments, edits, etc. A piece of metadata could be used to increase the usefulness of a document because it can clarify and provide information to the owner of the document about its creation.

2. What is a model?

• A model is the representation of a photograph in bits.

3. What's the difference between a raster image and an ASCII representation of a text document?

• A raster image, or bitmap representation is an image representation based on a division into pixels. An image is represented by pixels (image split up into rows and columns), and each pixel represents a color or shade. The number of pixels the photo is split up into determines how much information is lost from the original image. An ASCII representation of a text document is an 8-bit (1 byte) code determined for each number and letter (alphabet based). The computer then interprets the string of bits based on the conventions that were used to create the document.

4. What are filename extensions? What are they used for?

• Filename extensions are the three letters after the dot at the end of a filename that indicate how the contents (strings of bits) are meant to be interpreted. The purpose is to "tell" the computer how to read the information, like if the bits are colors, letters, or numbers. (ex. .pdf, .doc, .jpg, .gif)

5. What is lossless representation? What is lossy representation? What are the trade-offs in using each representation?

• Lossless representation allows the the exact same image to be rendered. Lossy representation allows an approximation to the same image to be rendered, there are only minute differences that human eye is usually not able to see. Lossless representations use more bits, so they take up more space. Lossy representations don't use up as much space because they use fewer bits.

6. What is steganography and what is it used for? Describe in your own words the steganography algorithm used in the activity.

• Steganography is the art of sending secret messages or information in ways that are discrete and don't look suspicious. It's effective because it conceals the information from other people that don't know what to look for in order to figure out the message. The steganography algorithm used in the activity used a sentence to encode a secret message. They used the first letter from each word to represent a string of 8-bits to represent a letter.

7. What would you have to do to delete a document from your computer so that it could not possibly be read by anyone else?

• In order to delete a document from the computer so that it couldn't be read by anyone else, one would need to have a computer programmed to over-write the blocks instead of putting them into the pool, by zeroing them out.

8. What is free and open source software? Provide an example.

• Free and open software is a licensed software that enables users and programmers to make changes to a software's code. An example is App Inventor and Python.

Free Response:

1. How has retouching become a controversial issue? Give an example.

• Retouching has become a controversial issue because images can now be easily altered, which leads to people questioning the reality of certain images. It has become especially controversial in court because the pictures being used for a case could be altered in order to skew the opinion of the jury.

2. Would you rather own a camera (or camera phone) with a higher number of megapixels or lower? Explain.

• I would rather own a camera with a high number of megapixels because the quality and crispness of photos would be sharper, despite the fact that it takes up for storage. I usually don't use much storage with the other apps on my phone, so I would rather have high quality photos than more apps.

3. Other than digital images, what might be an example of a computer model? Explain your answer based on the definition of a model.

• An example of a computer model is a CD. The same process occurs for a CD and a photograph: the model is rendered in order to create the final product. In other words, the bits representing the music are transferred onto a disk to create the final product of audible music from the digital representation. (model can be bits representing music too).

4. The code that implements App Inventor is open source and its impact on education is obvious. Find another example of open source software and describe its positive impact on education, business or society.

• Another example of an open source software is wikipedia. Through wikipedia, people are able to edit the information on each page for free. Wikipedia has shaped education because it provides students with easily accessible information to help them learn new concepts and study.