AP Computer Science Principles Vocabulary
Terms in this set (296)
allows programmers to specify the conditions under which a statement is executed.
one of the three control structures; tells the computer to make a decision before selecting the next instruction to process; also called the decision structure
Binary Digit. Single unit of information on a computer. Represented as a 0 or 1
The number of bits that are conveyed or processed per unit of time
A set of rules governing the exchange or transmission of data between devices. A set of rules for sending, receiving, and interpreting binary messages
The time it takes for a signal to arrive. Time units such as, miliseconds, seconds
Transmission capacity, measured by bit rate
Information for which only two answers are possible
Method of transmitting data that utilizes light
Method of transmitting data that utilizes electricity
A wireless networking technology that utilizes radio waves to transmit information/data
Request for Comments (RFC)
Documents that define and publish the standards and protocols for all to see on the Internet Engineering Task Force website
A preliminary sketch of an idea or model for something new. It's the original drawing from which something real might be built or created.
A number assigned to any item that is connected to the Internet. Every device connected to the internet is assigned an Internet Protocol address
Small chunks of information that have been carefully formed from larger chunks of information.
A computer which receives messages travelling across a network and redirects them towards their intended destinations based on the addressing information included with the message.
Transmission Control Protocol (TCP)
Provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
Domain Name System (DNS)
An abbreviation for Domain Name System, the Internet's system for converting alphabetic names into numeric IP addresses. Web sites using names, such as example.com
Hypertext Transfer Protocol (HTTP)
The protocol used by the World Wide Web. It describes how messages are formatted and interchanged, and how web servers respond to commands.
Reducing information and detail to focus on essential characteristics.
A computer that awaits and responds to requests for data.
A computer that requests data stored on a server.
The principle that Internet service providers should enable access to all content and applications regardless of the source, and without favoring or blocking particular products or websites.
The control or suppression of what can be accessed, published, or viewed on the Internet. It may be carried out by governments or by private organizations at the behest of government, regulators, or on their own initiative.
Vertex; Represented by a labeled circle
A line connecting two nodes
Weight; The number associated with an edge that indicates distance, time, or estimated cost
A set of edges that begin at one node and can be followed through other nodes back where you started
A set of edges that connects nodes together in a way that does not form a cycle.
The lowest weight path between two nodes
A measure of the number of steps per input size needed to complete an algorithm
A data table stored in a router that lists the routes to particular network destinations
Minimum Spanning Tree
Dictates the shortest aggregate path from one node to every node
A spanning tree connecting all nodes together with the minimum aggregate value of its edges.
Shortest Path Tree
A spanning tree connecting a source node to all others using the smallest values possible.
Internet Engineering Task Force (IETF)
A group of volunteers, private citizens, government officials, etc. who promote internet standards
Networks that are designed to connect similar computers that share data and software with each other.
An extranet is made available to ____ connections that have been granted an ____ _____ to the resources in the extranet.
Requires no username or password
Censorship of digital information (DI)
Commercial & governmental censorship of DI raise ethical and legal concerns.
Open source software
Software that results from the voluntary collaboration of developers who create programs that they distribute free to others
Licensing of software
Open source and Licensing of software and content raise ethical and legal concerns.
Aggregation of Information
consolidation of information, such as geolocation, cookies, browsing history, raise ethical and legal concerns.
Anonymity in online interactions
can be enable through the use of online anonymity software and proxi servers
exploitation of information
technology enables an act that exploits or victimizes someone (treats them unfairly)
server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers.
How information and content is presented
Companies target specific groups like teen or elders, etc.
Refers to intangibles such as ideas, music, art, photos, logos, movies, and programs that are the result of creativity and intellectual effort.
An exclusive right granted by the federal government allowing the owner to reproduce and sell an artistic or published work.
digital millennium copyright Act
1998 act that criminalized the circumvention of any anti-piracy encryption technology on commercial software, eBooks, videos, and music. It bans the sale and manufacture of devices used to illegally copy digital content.
a form of computer networking or other communication that uses radio signals and microwaves to transmit data
A term used to describe the discrepancy between people who have access to and the resources to use new information and communication tools, such as the internet, and people who do not have the resources and access to the technology.
A person's position in society as determined by income, wealth, occupation, education, place of residence, and other factors
Fundamental facilities and systems serving a country, city, or area, as transportation and communication systems, power plants, and schools
related to business
A program that allows the user to find and view pages on the world wide web.
Computers that link individual personal computer users to the Internet are called:
a process of reducing a file's size by altering and/or eliminating some pixels
A compression technique that is able to reconstitute all of the data in the original file; hence "lossless" means that this compression technique does not lose data
Internet Service Provider
An automated method of recognizing a person based on physical characteristics. Among the features measured are face, fingerprints, hand geometry, iris and voice
High level programming
Provides strong abstraction from the hardware and allows a program to be written in a language that can run on multiple types of computers.
Visual by humans.
Visual Basics, Python, Java.
English type language for programming.
Differentiates the language from assembly language and binary which are technically also programming languages
written to correspond closely to a computer processor's circuitry, a programming language that a computer can interpret quickly but that bears little resemblance to human language.
One that corresponds closely to a computer processor's circuity. (e.g., Machine Language).
are closer to the hardware than are high-level programming languages, which are closer to human languages
Abbreviation of central processing unit. The CPU is the brains of the computer. Sometimes referred to simply as the processor or central processor, the CPU is where most calculations take place.
(Central Processing Unit) The key component of a computer system, which contains the circuitry necessary to interpret and execute program instructions
When a programmer strings together a group of similar programs.
Representing or storing information with methods that separate layers of concerns so that the programmer can work with information while ignoring lower-level details about how the information is represented.
The processing of several aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.
is the concept of being able to look at programming code, identify a block of repetitive programming statements, and place them within one procedure that can be referenced by many objects, thus making the code easier to understand and reuse.
A pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept
The RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red(0-255), green(0-255), and blue(0-255).
Huffman coding is a lossless data compression algorithm. The idea is to assign variable-legth codes to input characters, lengths of the assigned codes are based on the frequencies of corresponding characters. The most frequent character gets the smallest code and the least frequent character gets the largest code.
are made up of binary sequences that are sent through the lowest layer of OSI
Open source interconnection
What does the acronym "OSI" stand for?
an electronic circuit that performs a Boolean function.
AND, OR, NOT
Router. In packet switching networks, routing is the higher-level decision making that directs network packets from their source toward their destination through intermediate network nodes by specific packet forwarding mechanisms.
____ is the ability to share physical resources, such as a printer or storage device, as well as logical resources, such as software and information.
What process secures a wireless network by protecting data packets being transmitted?
scrambling the data in a message in a systematic way in order to prevent competitors from electronically monitoring confidential data transmission
A very high speed transmission path that carries the majority of network data. Connects small networks into larger a structure or server nodes to a network where the majority of client computer are attached.
Malicious software created specifically for the purpose of infiltrating or damaging a computer system without the user's knowledge or consent includes a variety of technologies, including viruses, Trojan horses, worms, spyware, and adware
Data vs Information
Data are raw facts; information is data converted into a meaningful & useful context for decision making
a process that can be applied repeatedly
A device used to remove contamination from a fluid.
Identifying patterns in data based on common temporal (time) or spatial (geographic) traits is based on what type of data mining analysis?
System of organizing data according to its sensitivity. Common classifications include public, highly confidential, and top secret.
Creative Expression (Digital)
Refers to participation in a range of activities that allow for creative and imaginative expression
Problems with Data gathered during testing
A class of maps that use sophisticated software to create dynamic computer maps, some of which are three dimensional or interactive.
pulling out information
Online Collaborative tools
Helps with gathering and processing info
refers to finding a collection of symptoms that tend to go together, and not just seeing a single symptom
The number of different digits or combination of digits and letters that a system of counting uses to represent numbers.
A basic unit of information in computing and digital communications. Can have only one of two values. A 0 or 1
Creative development process
Employing non traditional techniques, combination of artifacts, or tools.
Represents values using numbers 0-9 and letters A-F
Discrete, discontinuous representations of information or works, as contrasted with continuous, or analog signals which behave in a continuous manner, or represent information using a continuous function.
programming, integrated IDES, spreadsheets, etc
Language of computers, examples: Java, Python, C, C++
Real Numbers (Floating-Point)
Formula representation of an approximation of real numbers
Levels of Abstraction
Different programming languages offer different levels of human to computer communication
Programming language similar to human language. Uses multiple abstractions to manage complexity
Most general concepts on top of the hierarchy and specific concepts on the bottom
programming language similar to machine code
Artifact, usability, functionality and sustainability of true artifact
Joint effort by more than one person to achieve a goal
Ability to either handle increasing workloads or to be easily expanded to manage workload increases. In a software context, systems that aren't scalable often require significant rewrites or the purchase or development of entirely new systems.
Digital Data Representation
Digital Representation of Information. Digital encoding of information means the data is stored in discrete units -- effectively numbers -- and it is contrasted with analog encoding which uses a physical quantity, e.g. charge, varying over a continuous range.
programs and other info used by a computer
Used to represent digital data.
Data about data.
Provides information about the content of a digital item e.g. each digital images from a digital camera has a file attached listing such things as date, time camera and shutter speed
something created by a human using a computer.
used software development utility used to maintain computers.
Represents values using 0 and 1
Lossy data compression
losses ability to reconstruct compressed data
A number that can have a fractional part
data file formats
data stored in multiple formats based on data characteristics
arise when personal data
concern for protection of info
affects methods and costs of manipulating data
precise sequence of instructions
application of each step of an algorithm
determines which part of algorithm used
uses Boolean condition to select algorithm used
repetition of part of an algorithm
notation of simplified programming language
describe algorithms so humans can understand them
time program takes to run
number of algorithm steps less than or equal to size of the input
exactly what is says
exactly what is says
defined by Manuel Castells as a set of interconnected nodes without a center
Standard protocol used on many LANs and on the Internet. See TCP.
Domain name system
Converts IP addresses into domains
A number that uniquely identifies each computer or device connected to the Internet.
Internet Protocol version 4. represents each IP Address as a 32 bit-binary number. 2^32
Hypertext Transfer Protocol. A conventional set of communication rules for controlling how Web browsers and servers pass information back and forth over the Internet.
The Internet Engineering Task Force develops and promotes Internet standards.
A group organized by rank
Domain name syntax
The process of determining the best path from Point A on one network to Point B on another is known as ____
possible to make single algorithm that is always correct
impossible to construct a single correct algorithm that always outputs yes or no
the delay before a transfer of data begins following an instruction for its transfer.
provides a framework for delivering security mechanisms. must include implicit or explicit validation of an entity's identity or the characteristics necessary for a particular event or transaction to occur.
the state of being protected against the criminal or unauthorized use of electronic data, or the measures taken to achieve this.
the use of computer technology to disrupt the activities of a state or organization, especially the deliberate attacking of information systems for strategic or military purposes.
DDoS Distribute denial-of-service
the intentional paralyzing of a computer network by flooding it with data sent simultaneously from many individual computers.
the fraudulent practice of sending emails purporting to be from reputable companies in order to induce individuals to reveal personal information, such as passwords and credit card numbers.
a piece of code that is capable of copying itself and typically has a detrimental effect, such as corrupting the system or destroying data.
computer software used to prevent, detect and remove malicious software.
a part of a computer system or network that is designed to block unauthorized access while permitting outward communication.
the art of writing or solving codes.
The secret key is used for both encryption and decryption of messages,
Public Key Encryption
technique that uses a paired public and private key (or asymmetric key) algorithm for secure data communication.
is an entity that issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate.
a new method, idea, product in the computing world.
Email; SMS; chat
new methods of communication.
a face-to-face conversation held over the Internet by means of webcams and dedicated software.
solutions close to to the real solution (approximate)
End to end architecture
Facilitates connecting new devices and networks on the internet
Make up internet are connected and communicating using addresses and protocols
The symbols +, -, *, /, %, and ^ used to denote addition, subtraction, multiplication, division, percentage, and exponentiation in an Excel formula
This invention make it possible for people to work from home, to send information to different places, and made the economy mor dependent
________ are programs that run on a server-tier computer and that manage HTTP traffic by sending and receiving Web pages to and from clients
____ is a method of encrypting TCP/IP transmissions above the network layer.
information-search services, such as Microsoft's Internet Explorer, Firefox, and Google Chrome, that offer detailed organizational maps to the Internet.
must scale to solve problems
Home PC on scientific research
Harnesses control and makes use of it
Enhances human capabilities
A substring of a string is another string that occurs "in". For example, "the best of" is a substring of "It was the best of times". This is not to be confused with subsequence, which is a generalization of substring. For example, "Itwastimes" is a subsequence of "It was the best of times", but not a substring.
Transmission Control Protocol
is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets between applications running on hosts communicating by an IP network. Major Internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP. Applications that do not require reliable data stream service may use the User Datagram Protocol (UDP), which provides a connectionless datagram service that emphasizes reduced latency over reliability.
breaks up digital information into individually addressed chunks
A method for expressing mathematically a logic circuit
concepts with clearly defined rules for membership
Real numbers (floating-point)
Real numbers are approximated by floating-point representation that do not necessarily have infinite precision
whole numbers and their opposites
Self Identifying variables
Locating and correcting errors in a program is called debugging the program
are standards made available to the general public and are developed (or approved) and maintained via a collaborative and consensus driven process. "Open Standards" facilitate interoperability and data exchange among different products or services and are intended for widespread adoption.
Correcting errors in software.
Connections between two or more computer systems
List of steps, such as assessments and interventions, to be taken in different situations.
strings; string operation
a contiguous sequence of symbols or values, such as a sequence of characters or a sequence of binary values
a whole number; a number that is not a fraction.
a series of interconnected things or events
The degree to which a system performs its intended function
Internet and web have impacted productivity positively and negatively in many areas.
A process in which a complex programs functions are portrayed and described in order for someone else to make sense of what is going on later, or just to describe what the program is doing and where it is doing it. ALSO describes the inputs, outputs, and processing logic for all program modules
consists of a series of steps programmers use to build computer programs
Online shopping, amazon, buying online and on site transactions conducted electronically.
Descriptions of the way work is to be done
limits, characteristics of a population
Internet vs. WWW
Enhanced methods of an opportunity for communication and collaboration.
Redundancy of routing
is a computer networking protocol that provides for automatic assignment of available Internet Protocol (IP) routers to participating hosts. This increases the availability and reliability of routing paths via automatic default gateway selections on an IP sub-network.
Justification ca include a written explanation about how a program meets its specifications
is an artifact, a document, diary, manuscript, autobiography, a recording, or any other source of information that was created at the time under study
Online Databases/ Virtual Libraries
is a collection of resources available on one or more computer systems, where a single interface or entry point to the collections is provided.
concerned with or engaged in commerce.
the basic physical and organizational structures and facilities (e.g., buildings, roads, and power supplies) needed for the operation of a society or enterprise.
relating to or concerned with the interaction of social and economic factors.
the gulf between those who have ready access to computers and the Internet, and those who do not.
a new method, idea, product, etc.
using radio, microwaves, etc. (as opposed to wires or cables) to transmit signals.
Digital Millennium Copyright Act
a 1998 US law intended to update copyright law for electronic commerce and electronic content providers. It criminalizes the circumvention of electronic and digital copyright protection systems.
are files that can be executed by an operating system to run in memory as a process and perform a useful function.
login is a process that allows a user to login to a website anonymously
Censorship (of digital info)
the suppression or prohibition of any parts of books, films, news, etc. that are considered obscene, politically unacceptable, or a threat to security.
defined as the amount of data that can be transmitted in a fixed amount of time. expressed in bits
a series of steps by which resources are changed into a desired product
Grids, Buildings, Transportation, facilitating human capability.
The process of identifying an individual, usually based on a username and password.
A network of computers configured to allow certain files and folders to be shared with everyone or with selected users.
when you give the computer a program and some data and tell the computer to follow the instructions in the program, you are running, or executing, the program on the data
A system or organization in which people or groups are ranked one above the other according to status or authority.
Google's track record of maintaining excellent performance while dramatically increasing the number of simultaneous users accessing its systems best exemplifies what network/system attribute?
a method of transmitting or receiving data (especially video and audio material) over a computer network as a steady, continuous flow, allowing playback to proceed while subsequent data is being received.
unnecessary repetition of data
Internet Engineering Task Force
Internet Engineering Task Force. A large international group concerned with the evolution of the Internet architecture and its smooth operation. DEVELOPS STANDARDS
Facilitate new ways of interacting with the environment and with physical systems.
copy (data) from one computer system to another, typically over the Internet
A program development plan intended to avoid debugging by adding and testing only a small amount of code at a time. it also helps create large correct programs.
The process of determining the best path from Point A on one network to Point B on another is known as ____
The process of determining the best path from Point A on one network to Point B on another is known as ____
Hypertext Transfer Protocol
is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. As soon as a Web user opens their Web browser, the user is indirectly making use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols (the foundation protocols for the Internet).
Application Program Interfaces Libraries
An interface that allows applications to make use of the operating system
IP address lookup, location, proxy detection, email tracing, IP hiding tips, blacklist check, speed test, and forums
Of or relating to commerce
Internet Protocol version 6
represents each IP Address as a 128 bit-binary number. 2^128
a process based on repetition of steps and procedures.
Changed how humans traveled navigate and find information related to geolocation.
a process that leads from an original formulation of a computing problem to executable computer programs. This includes: designing, writing, testing, debugging, and maintaining the source code of computer programs.
number of transistors per square inch on integrated circuits had doubled every year since their invention
Provide Widespread access and enables solutions to identified problems.
Foster new ways to communicate and collaborate. It has also introduced new data-security concerns
Special communications instructions that direct the travel of packets over the Internet are called
this search method starts at the beginning of the list and compares each element in turn with the required value until a match is found or the end of the list is reached.
Face book, Twitter, Blogs, Blogs, Have enhanced dissemination.
credibility of sources
how true they are
illegally copying information
source gotten one step removed
Creative Commons License
is used when an author wants to give people the right to share, use, and build upon a work that he has created.
ideas/inventions protected by patent
curation of info
advertising to select group
a series of names or other items written or printed together in a meaningful grouping or sequence so as to constitute a record sequence so as to constitute a record
finding weaknesses in system
empirical analysis of an algorithm is done by implementing the algorithm and running it on different inputs
aggregation of information
a sum/total of a lot of info
The computer execution of program instructions performed in the sequence established by a programmer
this can decrease the size and complexity of tasks required.
Open source software
can be used by anyone
licensing of software
need to purchase/get permission to use
Lossless data compression
reduces number of bits but still retains perfect detail
Domain name syntax
is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are formed by the rules and procedures of the Domain Name System (DNS). Any name registered in the DNS is a domain name.
A type of display device that includes a touch-sensitive face to accept input from the user. (3)
A touch sensitive surface that allows the user to select, control or move objects by touching icons and symbols using fingers
A ____ is an input device that uses a monitor or LCD panel as the backdrop for input options.
Discrete data which can be counted.
This is discrete data that has exact values, such as exam grades (A, or B, or C... There is no level in-between)
Analog data is represented using an infinite scale of values.
The representation and measurement of the performance or behavior of a system by continuously variable physical entities such as currents, voltages and so on.
The illegal copying and distribution of software.
Representations of real situations; give organizations the opportunity to speculate as to what would happen if certain courses of action were pursued.
Small text files that are sent to your computer from certain websites. They track your behaviour and transactions.
A small text file placed on your computer when you visit a Web page. Used to remember you or your preferences when you revisit that page or to track your browsing activities, cookies facilitate virtual shopping carts, page customization, and targeted advertising. They are not programs and cannot read your hard drive or cause damage to your computer.
a piece of writing that has been copied from someone else and is presented as being your own work.
A ratio such as 5:1 that indicates the ratio of compression that has been applied to a file. High compression ratios such as 35:1 indicate more compression so data can be contained in smaller files.
Summarizes the reduction in size of a file. Can be expressed two different ways, as follows. If more than 1, the compression ratio tells how many times bigger the original file is. If less than 1, the compression ratio tells the percentage by which the original file size has been reduced. A compressed data divided by original data
Institute of Electrical and Electronics Engineers
The Institute of Electrical and Electronics Engineers, an international nonprofit organization that sets standards FOR COMPUTING...
Instructions that specify the sequence in which a program is to be executed: sequence, selection, and repetition controls
a set of statements that execute in the order that they appear
enables a program to perform one or more actions as long as a certain condition is met
a loop that has been put within another loop
A logical error in which a repetition statement never terminates.
A loop in which the terminating condition is never satisfied.
An iteration structure that repeats one or more statements a specified number of times
A control flow statement that allows code to be executed repeatedly.
Uses a variable called a counter to control the number of times a set of statements will execute. Often called definite repetition because number of repetitions is known before the loop begins executing. Used on Nested logic
Binary search algorithm
Start in the middle and eliminate half the stack and keep looking in the middle. The data is pre-sorted.
The process of examining a middle value of a sorted array to see which half contains the value in question and halving until the value is located.
A type of group policy processing that allows a user to log on and see the desktop while policies are still being processed.
Method of processing multiple scripts at the same time without waiting for the outcome of a previously launched script to occur.
"QR codes or Quick Response codes are matrix barcodes, which store data such as URLs, geotags and links, that provide a way to link to online services using a camera and QR reader. QR codes can be read quickly by a mobile phone and provide information such as discounts and details of an event, a business or location. Data can be stored horizontally and vertically, making it capable of holding more data than a traditional bar code which only stores data in one direction
A popular URL shortening site that condenses long URLs into short ones under the bit.ly domain (which happens to use the Libyan country code "ly." Users can also create a custom name as long as it has not been taken; for example, the Bitly link to a video of this product on YouTube is bit.ly/CDEhistory.
Read more at http://www.yourdictionary.com/bitly#6hlQ1dH4O0c9RM1k.99
Portable Network Graphics
This supports advanced transparency, has a relatively average file size, and can be interlaced, optimizing for internet use.
A raster file that supports transparency and is best used for line art, logos, photographs and web but is not suitable for print.
A stand-alone power system (SAPS or SPS), also known as remote area power supply (RAPS), is an off-the-grid electricity system for locations that are not fitted with an electricity distribution system. Typical SAPS include one or more methods of electricity generation, energy storage, and regulation.
What is the program that appears to be a legitimate application, utility, game, or screensaver and that performs malicious activities surreptitiously?
masquerades as beneficial program while quietly destroying/damaging your system
Similar to a virus, but it has the capability to travel without any human action so it can infect many computers. It is able to replicate itself and can use the email address book to send itself to everyone listed. It consumes system memory to do this and slows down the computer or the network.
Process of converting readable data into unreadable characters to prevent unauthorized access.
a logic circuit whose output is 1 when at least one input is 1.
Logic circuit whose output is 0 when all inputs are 1
When someone pretends to be someone else with the intent of obtaining unauthorized data.
is a file extension associated with images, used in applications such as Pixlr.
The most common graphic file type, has full color graphic format, and has a relatively small file size.
Any variable, from the domain of Boolean algebra, having one of only two values
The Digital Millennium Copyright Act (DMCA) is a United States copyright law that implements two 1996 treaties of the World Intellectual Property Organization (WIPO).
VRRP (VIRTUAL Redundancy Routing Protocol)
(VRRP) is a computer networking protocol that provides for automatic assignment of available Internet Protocol (IP) routers to participating hosts. ... The physical router that is forwarding packets at any given time is called the master router.
having multiple backups to ensure reliability during cases of high usage or failure. Router - A type of computer that forwards data across a network. Redundant routing is impossible if there is only one possible path from one device to another.
Byte Pair Encoding
Byte pair encoding or digram coding is a simple form of data compression in which the most common pair of consecutive bytes of data is replaced with a byte that does not occur within that data.
Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plain text and decryption of cipher text. The keys may be identical or there may be a simple transformation to go between the two keys.
the practice of obtaining information or input into a task or project by enlisting the services of a large number of people, either paid or unpaid, typically via the Internet.
Domain internet vs Sub domain (second, third, fourth,, level domains)
For instance, http:// sub.example.com
http is the protocol
sub.example is second level domain
com is top level domain