csp stuff

what values does a bit store

a single digit- 0 or 1

how much bits is one byte

8 bits

what digit of a byte has the smallest value

the right most bit (1)

what happens if a number/calculation is too big to fit in the available bits? (255 for a byte)

overflow

when do round off errors happen

they happen with decimal (floating point: how computers store decimal numbers. Cannot always be exact, especially for tiny or repeating decimals, which causes round-off errors) numbers. output might be a tiny off do to rounding

examples of round off error

1/3 =0.33

15×2=29.999996

15×2=30.000004

what does the base of a number system tell you

•  how many digits it uses before it has to carry over to the number place value. 

  • Base 10 is decimal AKA what we use everyday: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

  • Base 2 is binary AKA what computers use: 0, 1

what is analog data

• continuous and has infinite possible values between any two points. This is for real-world signals and harder to store perfectly.

• When computers record analog data, like real-life sound, they sample it (taking snapshots at regular intervals. More samples = better quality, requires more storage.)

  • Sampling rate is how often you sample the data and higher numbers mean more accuracy, bigger file

  • Resolution is how many samples total, more detail, more storage (think high resolution is like super sharp while low resolution is all blurry). If it asks about smaller spacing between samples, then that causes more samples which causes better detail

Meanwhile, digital/binary data is discrete (stepped), has finite values, binary (0s and 1s), and is

lossless compression

• No information is lost-- you can perfectly reconstruct the original data from the compressed file.

  • Often used for when you need perfect accuracy like text files

  • Includes things like color inversion in photos

lossy compression

• is when some data is permanently discarded to make the file smaller. You cannot recover the original file exactly, just a close approximation. This is when file size matters more than perfect quality (though generally it only removes parts of data that are considered les noticeable or important to human senses) so like streaming music or video or uploading images or storing lots of files.

  • Also includes things like color scaling like gray or red scale 

fair use

allows limited use of copyrighted (they are the intellectual property of the creator) materials for purposes like criticism, comment, news reporting, teaching, or research

creative commons

• The licenses differ in whether they also require these conditions:

  • Share Alike: The reused work must be licensed using the same CC license as the original work.

  • Non-Commercial: The reused work can only be used for non-commercial purposes.

  • No Derivates: The original work can be distributed and displayed, but it cannot be modified.

  • Example: creative commons attribution license

    • This license enables reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use. CC BY includes the following elements: BY: credit must be given to the creator.

    • Creative commons license for Public domain (not copyrighted, the creator waives): waives all rights of the creator and places their work in the public domain--anyone can use the work for any purpose w/o attribution 

    • Open source licenses (copyrighted w/ permissions) give the user the right to view, modify, and distribute the software, but often require attribution.

the goal of the open access movement

• to remove barriers to scientific information, by encouraging journals to freely distribute full research papers online and encouraging authors to archive their papers in an open access repository or personal website.

a creative work in the public domain

no longer protected by copyright law and free of copyright restrictions. Anybody can use and reuse that creative work in any way, and they do not have to provide attribution

computing device

a physical device that can run a program. isn't just a computer—it's any device that can run a program, such as a tablet, phone, or smart sensor.

what are some numerical values a sequence of bits can represent

 positive numbers, negative numbers, or fractions

computer network

any group of interconnected computing devices capable of sending or receiving data.

a group of connected computing devices that can share resources and information w/ each other

internet

global network of interconnected networks that uses standardized communication protocols to connect devices and systems around the world, allowing them to exchange data and information. This is the largest computer network. It can be connected wirelessly

a domain name

•  the human-readable address of a website (www.google.com). It is easier for people to remember and type than a numerical IP address.

  • Easy-to-remember website name

IP address

• a unique string of numbers that identifies a device on the internet. Every device connected to the internet has one.

  • The Internet Protocol (IP) is the protocol that describes how to route messages from one computer to another computer on the network. Each message is split up into packets, and the packets hop from router to router on the way to their destination

  • Numerical label used to locate a device on the internet 

• The Internet Protocol (IP) describes both an addressing scheme (which assigns IP addresses to Internet-connected devices) and a routing strategy (which routes messages based on destination IP address).

what does the internet use DNS for

• (Domain Name System) to translate domain names into IP Addresses.

  • System that translate domain name into IP addresses

router

• a device that forwards data between networks, using IP addresses

  • The router's job is to look up the destination IP address in their forwarding table, determine the next router that will get the packet closer to its destination, and send the packet to the router.

how does data travel

• Data travels from your device to the server using the IP address. Data is broken into packets and sent through various routes to reach the destination.

IPv4 vs IPv6

• IPv4 is older internet address system, limited supply; IPv6 is newer system with way more addresses available 

hexadecimal

• base-16 number system. It is a shorter way to represent binary since 1 hex digit = 4 bits. It is more compact and readable. It is often used in colors in web design and IPv6 addresses. A is 1010, for example

  • Normal numbers + a few letters 

  • A = 10; B = 11; C = 12; D = 13; E = 14; F = 15

    • F is larger in value than A, for example (with hexa-decimal). 

bandwidth

• the maximum bit rate of a system.

  • Bandwidth is a measurement of how much data can be transferred in a fixed period of time. It's typically measured in multiples of bits per second, such as Kbps (kilobits/second), Mbps (megabits/second), and Gbps (gigabits/second).

bit rate

• Network connections can send bits very fast. We measure that speed using the bit rate, the number of bits of data that are sent each second

TRUE OR FALSE

• Routing on the Internet is dynamic. Each time a router receives a packet, it decides where to send it next based on a forwarding table and network conditions. That means that the next packet may follow a different sequence of stops.

true

The Transmission Control Protocol (TCP)

• a transport protocol that is used on top of IP to ensure reliable transmission of packets.

  • TCP includes mechanisms to solve many of the problems that arise from packet-based messaging, such as lost packets, out of order packets, duplicate packets, and corrupted packets.

  • TCP uses a three-way handshake to establish a connection. TCP includes several mechanisms to improve the reliability of transmission, such as the ability to re-send packets that were lost.

    • The TCP metadata helps with the reliability aspects of TCP, such as packet reassembly and packet retransmission. Specifically, TCP uses the sequence number in the metadata to reassemble packets in the correct order.

  • Since TCP is the protocol used most commonly on top of IP, the Internet protocol stack is sometimes referred to as TCP/IP.

how do the world wide web and internet relate

• When most of us talk about using the "Internet", we're typically talking about a specific part of the Internet: the World Wide Web (WWW, or simply, the Web).

what’s the WWW

• massive network of webpages, programs, and files that are accessible via URLs.

The WWW is a system of linked webpages (and associated resources such as audios, videos, and scripts). A directory of the Web would either list websites (e.g. http://wikipedia.org) or individual webpages (e.g.

The Hypertext Transfer Protocol (HTTP)

• used by the browser to tell the host computer what file it wants to retrieve

scalable system

• one that can continue functioning well even as it experiences higher usage.

  • Handles way more traffic/users, larger and more complex amounts of data, grows w/ demand without needing a total redesign

internet protocol suite

• the general name for the stack of protocols that make the internet work (like TCP/IP)

open (non-propriety) protocol

• is one that is not owned by any particular company and not limited to a particular company's products.

networking protocol

• an agreed-upon set of rules that describe how computing devices can successfully communicate in the network.

heuristic

a technique that guides an algorithm to find good or approximate choices when finding the exact solution would take too long.

• Often used when an optimal solution is too time-consuming to compute.

• Helps find a “good enough” or efficient solution more quickly.

• Common in optimization problems, AI, and real-world decision-making.

Example: A navigation app estimating a fast route based on traffic patterns, even if it’s not the absolute shortest.

undeciciable problem

• problem is one that should give a "yes" or "no" answer, but yet no algorithm exists that can answer correctly on all inputs.

a MOD b

returns the remainder of a/b

ASCII

 character encoding system (like letters, digits, and symbols). They r represented using 8 bits (each character). Only encodes English characters w/ 128 possible values

abstraction

• the process of reducing complexity by hiding unnecessary details and showing only the essential features

when do u write return

• In psuedocode, you write the return before the final closing curly brace of a function/procedure.

paralle vs distributed computing

• a computational model that splits a program into multiple tasks so that it can run some tasks simultaneously. It is particularly helpful when a program is too slow to run sequentially.

• Distributed computing is a computational model that uses multiple computing devices to run a program. It can be very helpful since the additional devices would provide more storage space for the digital files.

software modularity

the practice of organizing code into multiple modules, each of which is responsible for a different aspect of the software.

append

Adds item to the end of list, increasing the length of list by 1.

symmetric encryption

• 
  

  • Same key (private key) is used to encrypt and decrypt data.

  • Faster, but less secure if the key is intercepted.

  • Example: Caesar Cipher, Vigenère Cipher, AES.

• Asymmetric Encryption (Public Key Encryption)

• • Uses a public key to encrypt and a private key to decrypt.

  • More secure, used in internet communication (e.g., HTTPS).

  • Example: RSA algorithm.

• One key total

• The same key is used for both encryption and decryption.

• That key must be shared secretly between the sender and the receiver.

ASCII

(American Standard Code for Information Interchange)

A character encoding standard for electronic communication, representing text using numbers.

• Each character = 7-bit binary number (e.g., A = 1000001 or decimal 65).

• Used to represent letters, digits, and symbols.

• Part of abstraction in how computers handle text.

• Helps show how data is stored and transmitted using binary.

Example Conversions:

• A = 65 = 1000001

• a = 97 = 1100001

• 3 = 51 = 0110011

Why It Matters:

Understanding ASCII shows how computers translate human-readable text into binary — essential for understanding text-based input/output.

packet metadata

Metadata in packets is extra information added to the actual data being sent. It helps computers know how to route, reassemble, and process the data correctly across networks.

🔸

What’s in Packet Metadata?

Think of it like an envelope around your message! Some key metadata fields include:

• Source IP address – where the data is coming from

• Destination IP address – where it’s going

• Packet number – helps reassemble data in the right order

• Protocol – tells the system how to read the data (e.g., TCP, HTTP)

• Error checking info – used to detect if data got corrupted

🔸

Where Is This Metadata Stored?

• Stored in the packet header — a section of the packet that comes before the actual data (called the “payload”)

• This header is added automatically by network protocols like TCP/IP

🔸

Why It Matters (AP CSP Focus):

• Enables reliable delivery of data over the internet

• Helps routers figure out where to send the data

• Supports fault tolerance: if packets are lost, the system can request a resend

• Makes streaming and downloads possible by splitting and reassembling data

Metadata in packets is extra information added to the actual data being sent. It helps computers know how to route, reassemble, and process the data correctly across networks.

🔸

What’s in Packet Metadata?

Think of it like an envelope around your message! Some key metadata fields include:

• Source IP address – where the data is coming from

• Destination IP address – where it’s going

• Packet number – helps reassemble data in the right order

• Protocol – tells the system how to read the data (e.g., TCP, HTTP)

• Error checking info – used to detect if data got corrupted

🔸

Where Is This Metadata Stored?

• Stored in the packet header — a section of the packet that comes before the actual data (called the “payload”)

• This header is added automatically by network protocols like TCP/IP

🔸

Why It Matters (AP CSP Focus):

• Enables reliable delivery of data over the internet

• Helps routers figure out where to send the data

• Supports fault tolerance: if packets are lost, the system can request a resend

• Makes streaming and downloads possible by splitting and reassembling data

metadata

Data that describes other data — it provides information about a file or dataset’s structure, format, or properties.

🔸

Examples of Metadata:

• A photo’s dimensions, resolution, and timestamp

• A text file’s name, size, and creation date

• A spreadsheet’s number of rows/columns, data types, or creator info

🔸

Where Metadata is Stored:

• Inside the file: Embedded within the file format itself (e.g., EXIF data in image files like .jpg)

• Alongside the file: In a separate file or database (e.g., a CSV file might have a separate JSON file describing its columns)

• In systems or platforms: Metadata can be managed and stored by apps, operating systems, or cloud services (e.g., Google Drive tracks metadata like owner, last edit date)

🔸

Why It’s Important (AP CSP Focus):

• Helps with organizing, sorting, and filtering data

• Makes data analysis and visualization easier

• Supports abstraction: you don’t always need to see full data — just info about it

• Common in large datasets, web pages, and media files

🔸

Fun Fact (AP CSP Tip!):

Metadata is especially helpful in big data projects — like finding trends in social media or cataloging millions of images — because it gives context without having to look at the raw data itself.