APCSP.CodeHS with JS.Unit 8-Digital Information (47)

binary

A base 2 system of numbers that represents data through 0s and 1s

Byte

8 bits

Overflow

When a number becomes too large to fit into the number of bits allocated

What happens when there is overflow

The computer will report an error and truncate the number (cap all results to the max number and lose data)

Encodings

A system in which certain sequences of bits represent different things. Computers that both understand an encoding can pass and open files between each other with it.

ASCII

American Standard system using 8 bits to store the alphanumeric and other characters

Unicode

Universal system using hexadecimal numbers to make character sets for languages -- a superset that includes ASCII

Analog data

Real world data, infinitely detailed

Digital data

Finite data in binary representation

Sampling

Taking a snippet of analog data at regular time intervals and storing it as digital data

Sampling rate

Number of samples in a second (how OFTEN)

Compression algorithms

Algorithms that reduce space needed to represent a file

Lossless compression algorithms

Algorithms that reduce the size without loss of information, so original data can be reconstructed

Lossy compression algorithms

Algorithms that reduce size by discarding non-important information, reducing size but affecting quality

Run-length encoding (RLE) algorithm

A type of lossless image compression in which the computer replaces each row with numbers that say how many consecutive pixels are the same color (3W, 4R, 3W) For black and white always starts with white

What should you consider when choosing how to compress

Consider scenario. If you need a picture for something important (big screen) you want high quality but if it is for a website you can use lower quality to allow faster download

Copyright

Licenses and rights that give owners the ability to determine if and when their work can be copied

Public domain

Works with expired copyrights (mostly expire after 70 years in the US) enter this, anyone can use and adapt without restriction. Can also declare work into the public domain

Fair use

Allows limited use of copyrighted materials for certain purpose by considering the purpose and character of use, nature of copyrighted work, how much work is used, impact of use, value of work

Digital rights management (DRM)

tools that restrict where and how a user can use copyrighted media (ex spotify has DRM layer that prevent users from listening to songs elsewhere)

The Digital Millenium Copyright Act (DMCA)

Criminalizes production and distribution of technology that is used to circumvent DRM. Copyright owners can use to send notices to and sue violators

Copyright licenses

Licenses that owners can apply to their work to lessen copyright restrictions so more people can use their work

Creative Commons

Offers 6 licenses that make sure an author is attributed

Conditions used in Creative Commons licenses

Share alike - reused work uses same license as original work.

Non-Commercial - reused work used non-commercially

No Derivatives - the original work cannot be modified

Open source licenses

Programmers can use them to make code publicly available for others to reuse it properly

Benefits of open source

Can write less code, try out many libraries, and support many developers who create the libraries

Bit width

How many bits are used to store sampled analog data (how MUCH)

Heuristic

A problem solving approach (algorithm) to find a satisfactory solution where finding an optimal or exact solution is impractical or impossible.

Kilobyte (KB)

about 1 thousand bytes

Megabyte (MB)

about 1 million bytes

Gigabyte (GB)

about a billion bytes

1,073,741,824 (2^30) bytes. 1,024 Megabytes, or 1,048,576 Kilobytes.

Terabyte (TB)

1,099,511,627,776 (2^40) bytes, 1,024 Gigabytes, or 1,048,576 Megabytes.

Petabyte (PB)

A Petabyte is 1,125,899,906,842,624 (2^50) bytes, 1,024 Terabytes, 1,048,576 Gigabytes, or 1,073,741,824 Megabytes.

Exabyte (EB)

1,152,921,504,606,846,976 (2^60) bytes, 1,024 Petabytes, 1,048,576 Terabytes, 1,073,741,824 Gigabytes, or 1,099,511,627,776 Megabytes.

Image

A type of data used for graphics or pictures.

metadata

Data that describes other data. Ex. A digital image may include metadata that describes the size of the image, number of colors, or resolution.

pixel

short for "picture element;" it is the fundamental unit of a digital image, typically a tiny square or dot which contains a single point of color of a larger image.

filetype

A name given to a specific kind of file that indicates how the bits contained in the file should be read. Examples are .pdf, .png, and .doc.

.jpeg

Stands for "Joint Photographic Experts Group." A popular image file format which is commonly used by digital cameras to store photos since it supports 224 or 16,777,216 colors. This format uses "lossy compression" by exploiting the eye's inability to perceive small colour details as well as small details of light-and-dark in an image.

.gif

Stands for "Graphics Interchange Format." This format is often used for line drawings and animations because of it's limited ability to represent colors (8 bit format which means the maximum number of colors supported by the format is 256.) This format uses lossless compression.

.mp3

audio file - lossy compression

.mp4

vidio file - lossy compression

.png

image file - lossless compression

.pdf

portable document format is a file format used to present documents in a manner independent of application software, hardware, and operating systems

.bmp

image file - lossless compression

.zip

an archive file format that supports lossless data compression of any type of file.

digital divide

the gulf between those who have ready access to computers and the Internet, and those who do not.

abstraction

Removing unnecessary details to focus on the essential characteristics. To break problems up into separate parts which can then be solved separately and recombined to form a complete solution. To focus on and use something based only on what it does and without concern for how that functionality is accomplished.

hexadecimal number system

A base-16 number system which consists of the digits 0-9 and A-F. Each of these symbols can occur in each place value position.