The Internet & Networks

AP CSP Key Terms (The main terms that appear frequently)

Abstraction

Hiding unnecessary detail to reduce complexity and focus on what matters. The higher the level of abstraction, the more detail is hidden. Example hierarchy from high to low abstraction: Animal → Person → Student → You. In programming, functions and procedures are tools for achieving abstraction.

Algorithm

A step-by-step set of instructions designed to solve a specific problem or accomplish a task. Algorithms are the foundation of all programming.

Binary Search

Starts at the middle of a sorted list, then eliminates half the remaining elements with each guess. Much faster than linear search but requires the list to be sorted first. Run time: log(n).

Linear Search

Checks every element in a list one by one until the target is found or the list ends. Does not require the list to be sorted. Worst case: n steps (checks every item).

Packets

Data sent over the Internet is broken into small chunks called packets. Packets may travel different paths, arriving in order, out of order, or not at all. Missing packets are re-requested and reassembled at the destination.

Routing

The process of finding a path from a sender to a receiver across a network.

Public Key / Private Key Encryption

Uses a pair of keys: a public key (shared openly) and a private key (kept secret by the owner). Data encrypted with the public key can only be decrypted with the private key. This means anyone can send you a secure message using your public key, but only you can read it.

Symmetric Encryption

Uses a single shared key for both encrypting and decrypting data. Both the sender and receiver must have the same secret key. The Caesar cipher is a classic example. Because only one key is used, it must be kept secret.

Parallel Computing

A program is broken into smaller tasks that run simultaneously. Total time = the sequential portions plus the longest of the parallel tasks. Efficiency is limited by whatever portion of the program must remain sequential.

Sequential Computing

Operations are performed one at a time, in order. Total time = the sum of all steps.

Lossless Compression

Reduces file size while allowing the original data to be perfectly reconstructed. No information is lost.

Lossy Compression

Reduces file size significantly but only allows an approximation of the original to be reconstructed. Some data is permanently discarded (e.g., compressed audio or blurry JPEGs).

Digital Divide

The gap between those who have reliable access to computers and the Internet and those who do not, often driven by income level, geography, or disability.

Bits

The smallest unit of data in a computer. A bit is either 0 or 1. 4 bits can store 16 values (0–15).

Bytes

8 bits. A single byte can store a maximum value of 255.

Overflow Error

Occurs when a program tries to store a number outside the range its memory can handle. For example, trying to store a value larger than 15 in a 4-bit space.

Phishing

A technique that tricks users into revealing personal information (passwords, account details) by disguising a request as trustworthy. Commonly done via fake emails or websites.

DDoS (Distributed Denial of Service) Attack

An attack that floods a website or server with so much traffic that it becomes unavailable to real users.

Metadata

Data about data. For example, a photo file is the data; its metadata includes the date taken, file size, and location. A book's metadata includes its author and publisher.

Bandwidth

The maximum amount of data that can be sent over a network in a fixed amount of time, usually measured in megabits per second (Mbps). Higher bandwidth = faster data transfer. Think of it as the size of a water pipe — the bigger the pipe, the more water flows through per second.

Latency

The time between sending a request and receiving a response. Unlike bandwidth, you want latency to be as low as possible. Measured in milliseconds. Think of it as how long it takes water to start coming out after you turn on the tap.

DNS (Domain Name System)

Translates human-readable domain names into IP addresses, allowing people to browse using names instead of numbers.

Crowdsourcing

Obtaining information, input, or work from a large number of people, typically via the Internet.

Citizen Science

Scientific research conducted with help from distributed volunteers, many of whom are not professional scientists, who contribute data using their own devices.

Reasonable Run Time

An algorithm's run time is considered reasonable if it grows no faster than a polynomial of n (the input size). Examples: n, n², n⁶ are all reasonable. Run times like n! or nⁿ are considered unreasonable because they grow far too fast to be practical.

Floating Point Imprecision

Computers store decimal values in binary, which cannot perfectly represent all fractions. This causes small rounding errors (e.g., 0.1 + 0.2 may not equal exactly 0.3 in code).

Creative Commons License

A licensing system that allows creators to specify how others may use their work. A no-rights-reserved license allows anyone to freely use, remix, or build on the content.

Heuristic Approach

A problem-solving strategy that uses practical shortcuts or educated guesses to find a good-enough solution quickly, rather than searching for the perfect answer. Commonly used in AI and optimization problems where exact solutions would take too long.