AP Computer Science Principles

Overflow

error that results when the number of bits is not enough to hold the number, like a car's odometer "rolling over"

Round-off

error that results when the number of bits is not enough to represent the actual number, like 3 digits to represent π as 3.14

Lossy

Compressing data in a way that throws some data away and makes it almost impossible to recover the original, great compression, like JPEG images

Lossless

Compressing data in a way that preserves all data away and allows full recovery of the original, good compression -- usually not as good as lossy, like PNG images

Metadata

data about data, like a camera storing the location, aperture, shutter speed, etc. for a digital photo

Sequencing

code flows line by line, one after another, like a recipe

Selection

a boolean condition to determine which of two algorithmic paths are taken, aka if-then

Iteration

using a looping control structure, like while, for, foreach, repeat, repeat-until, etc.

Reasonable Time

polynomial in the number of steps an algorithm takes in the worst case based on the input size

Not reasonable time

Usually exponential in the number of steps, like doubling every time your input grows by one

Heuristic

using a "rule" to guide an algorithm, like always walking toward the north star if you were stuck in a forest

Undecidable

A problem that is so difficult, we can't ever create an algorithm that would be able to answer yes or no for all inputs, like determining if a user's program run on some input would always stop and not run forever

Linear Search

Going one by one vs starting in the middle and going left/right like looking for a word in the dictionary

Binary Search

requires the list to be sorted in order and then cutting the list in half

APIs

Application Programming Interface

Citizen Science

Lots of people to help with a scientific project, like asking everyone around the world to count the butterflies they see one day

Cloud Computing

Using distributed calculations and/or storage for big data or a web application

Crowdsourcing

Asking lots of users online to help with something, like funding a project, or running SETI@Home to help look for extraterrestrial signals

Creative Commons

An alternative to copyright that allows people to declare how they want their artistic creations to be shared, remixed, used in noncommercial contexts, and how the policy should propagate with remixed versions

Open Access

A policy that allows people to have read access to things, e.g., libraries or online data

Moore's Law

The # of transistors on a chip doubles every two years

Peer-to-peer Networks

A system where one user's computer connects through the Internet to another user's computer without going through an intermediary "centralized" computer to manage the connection

Digital Divide

The idea that some communities / populations have less access to computing than others

ISP

Internet Service Provider

How does internet communication arrive at its destination?

Speech on the Internet goes from the source to an ISP, into the cloud, out of the cloud to another ISP, and to its destination

How can the government control speech on the Internet?

1) It can try to control the speaker or the speaker's ISP, by criminalizing certain kinds of speech. But that won't work if the speaker isn't in the same country as the listener.

How can Internet posters evaded being convicted for defamation/slander on the Web?

The posters could evade responsibility as long as they remained anonymous, as they easily could on the Internet.

UDP

User Datagram Protocol

HTTP

HyperText Transport Protocol

SMTP

Simple Mail Transport Protocol

What does "End to End" mean in regards to the Internet?

"End to End," in the Internet, means that the switches making up the core of the network should be dumb—optimized to carry out their single limited function of passing packets.

RFC

Request for Comment

Shortcut for going from binary to hexadecimal

To translate a binary numeral (like 11010111012) to hexadecimal, start by splitting it into groups of four bits, from right-to-left (like this: 11 0101 1101).

Internet

A network of independent but connected devices all over the world.

World Wide Web

The collection of interlinked website documents (such as HTML files) that you can view with a web browser by typing addresses like http://bjc.berkeley.edu/website/privacy.html.

HTML

Hypertext markup language

URL

Uniform Resource Locator

Server

A computer hosting data for others to access

Protocol

the standard for communication between browsers and servers (usually "http" or "https")

Domain Name

The name of the server that hosts the data

Path

the location of the data in a hierarchy of folders on the server

Protocols

Standards for communication

IP

Internet Protocol

Redundant

There are multiple pathways among the physical connections of the Internet to create redundancy. Even if one pathway is unavailable, there is still another way to transmit a message from sender to receiver

Hiearchial

There are two Internet addressing systems, domain names and IP addresses. These address __ works much like the postal system, which locates people first by state, then city, then street, then house number, then apartment, and then finally person.

Fault Tolerance

ability to work around problems

Scalability

the ability of the net to keep working even as the size of the network and the amount of traffic over the network increase.

Virus

A kind of malware that tries to spread itself over the network to other computers.

Antivirus Software

Helps protect against virus attacks

Phishing

An attacker sends you an email that appears to be from some official organization (such as your bank) and tricks you into giving information to the attackers (such as your bank password).

DDoS

Distributed Denial of Service

-Consists of sending a lot of requests to a server at the same time. This can overload the server's network bandwidth.

-Causes a temporary inability to reach the targeted server so other users of that server are denied service.

Which protocols are used to keep secure HTTP connections?

Transport Layer Security (TLS) or maybe an older version called Secure Sockets Layer (SSL)

Certificate Authorities

Used by many websites for encryption to protect files and information that is transmitted over the Internet. They issue certificates to verify the identity of a user or computer.

Public IP Address

The IP address that is logged by various servers/devices when you connect to them through your internet connection.

Private IP Address

An IP address that's reserved for internal use behind a router or other Network Address Translation (NAT) device, apart from the public.

IP v4

This address is big enough to support 2^32 computers. That's about four billion (4 · 109), but there are more than seven billion people on Earth, so there aren't enough IP addresses to go around. Each of the four numbers in a typical IP address today is an eight-bit byte with a value between 0 and 255

IP v6

The long-term solution is to increase the length of an IP address. The new IP addresses are 128 bits wide, which is enough to support 2^128 (about 1038) computers.

Routers

The "connection points" of the Internet.

Packets

When you send a message over the Internet, your computer divides it into small chunks called that it sends individually, each on its own path. A can include any kind of data: text, numbers, lists, etc.

Packet Switching Network

A digital networking communications method that groups all transmitted data into suitably sized blocks, called packets, which are transmitted via a medium that may be shared by multiple simultaneous communication sessions.

Hierarchy of Abstractions

Manages the complexity of the Internet by hiding the details of lower levels of the system. The highest level of abstraction includes the most general features of the Internet that have to work the same across all devices. At lowers levels of abstraction, things get more device-specific.

Application Layer Protocols

The highest level of abstraction because they manage how data is interpreted and displayed to users. These protocols give meaning to the bits sent by lower-level protocols; user and server computers must agree on what the bits mean, and application protocols (like HTTP) offer this.

Transport Layer Protocols

Manage the breakdown of a message into packets to be transmitted by lower level protocols and also the reconstruction of the message from the packets upon arrival.

Internet Layer Protocols

Manage the pathways that the data packets travel across networks. These protocols treat the Internet like one large network even though the physical reality on the lower level is one of many tiny subnetworks.

Network Interface Hardware

Also known as Link Layer

DNS

Domain Name System

Who is in charge of the Internet?

The computers on the Internet and the connections among them don't belong to any one organization.

ICANN

the Internet Corporation for Assigned Names and Numbers

For how long has the U.S. dominated the Internet and why?

The U.S. has "controlled" the Internet up until 2009. The Advanced Research Project Agency (ARPA) first developed the Internet in 1969.

Open Protocols

Standards that are not owned by a company

IETF

(The Internet Engineering Task Force) and the Internet Society oversee Internet protocols

What does the Internet rely on to operate properly?

The internet relies on the cooperation of many different elements.

Firewall

Used to limit the kinds of connections (HTTP requests, incoming mail, etc.) outsiders can make to your computer.

Cipher

The set of rules you are using to encode the information

Key

What tells you how to arrange the cipher's rules. _ is applied using an algorithm to a string or block of unencrypted text to produce encrypted.

Public Key

A code that is available for anyone to use.

Private Key

A code that must remain confidential to its respective owner.

How does Public Key/Private Key Cryptography work?

Example: If Bob wants to send sensitive data to Alice, and wants to be sure that only Alice may be able to read it, he will encrypt the data with Alice's Public Key. Only Alice has access to her corresponding Private Key and as a result is the only person with the capability of decrypting the encrypted data back into its original form. As only Alice has access to her Private Key, it is possible that only Alice can decrypt the encrypted data. Even if someone else gains access to the encrypted data, it will remain confidential as they should not have access to Alice's Private Key.

Encryption

Works by converting information or data into a language that cannot be understood in one glance. Usually, the information is sent to a person who can decrypt it using a key only they have access, keeping the information's privacy intact.

Authentication

Helps to verify that original author of the code is what he or she claims to be.

Integrity

Essential towards maintaining the privacy of the message because it must be known that the message was not tampered with in any way, shape, or form.

Non-repudiation

Where the user sends a message to another person but later denies he or she actually sent the message, causing confusion and bringing the integrity of the message into question.

Hash function

Types of systems where the user sends a plain text message to another user without a key. They are usually generated based on the message which helps determine whether the integrity of the message has been tampered.

AND

a Boolean operator. Both have to be true in order for it to evaluate to true.

OR

a Boolean operator. one or the other has to be true in order for it to evaluate to true.

NOT

a Boolean operator. Everything except the entered input is true.

Boolean Expression

an expression that results in a __ value, that is, in a value of either true or false .

Composition of Functions

An act or mechanism to combine simple functions to build more complicated ones.

Conditional Statement

Set of rules performed if a certain condition is met.

Data Type

A classification of data which tells the compiler or interpreter how the programmer intends to use the data. Examples include : real, integer, float (decimal point number)

Debugging

A multi-step process that involves identifying a problem, isolating the source of the problem, and then either correcting the problem or determining a way to work around it. The final step of is to test the correction or workaround and make sure it works.

Default Value

What the code is set to when it is started.

If () Clause

Keep Checking:

If () . . . Else Clause

Keep Checking:

Input Type

Set up different variables to take a specific _.

Lists

Reports a newly created _ with the given items.

Nested IFs

If you need to test for more than one condition, then take one of several actions, depending on the result of the tests, you can nest multiple IF statements together in one formula.

Script variable

Used when you only need a variable temporarily, during the running of a particular script. You can use ____ __ block to make the variable. Example : for loop, the (length) only works inside the for loop.