AP CSP - Unit 4

What is a bit?

a single unit of data that can only have one of two values; usually represent the two values with 0 (off) and 1 (on)

What is a byte

eight bits

What is a word

a sequence of however many bits the CPU processes at a time; usually either 32 or 64 bits

What is a binary sequence

a string of ones and zeros; can represent text, pictures, sound, and video

Difference between analog and discrete data

analog data has values that change smoothly, digital data has values that change in discrete intervals

Sampling

measuring values, called samples, of an analog signal at regular intervals

Sampling rate

number of samples measured per second

Width

the number of bits that a CPU processes at a time

Word

binary sequence of that many bits; most modern computers have 64 bits

What is an overflow error

when a number or operation result is too big,, an overflow error results

How do non-integer numbers get stored?

with a floating point number which is any numbers with decimals; scientific notation uses powers of ten to represent very large or very small values, floating point uses powers of two

What happens if a value exceeds the limitation of floating point values?

a round-off error occurs

How to translate from base 10 to base 2

1. find the largest power of two that is less than the number. Write out the binary place values from right to left

2. Subtract the largest power of two from the number

3. Record a 1 in that place for the power of two

4. Determine if the next power of two is less than or equal to the new remaining number. If so, repeat #2 and #3. If not, record a zero for that power of two

5. Repeat until you have a bit (0 or 1) for all places

Why compress data

the size of data affects the amount of time it takes to be sent, compression algorithms reduce the size of data

Lossless data compression

algorithms are reversible (there is no loss in quality), you can reconstruct the original data; works by removing redundant data

Lossy data compression

algorithms that are not fully reversible; you can reconstruct only an approximation of the original data; works by removing details that people aren't likely to notice

What is the internet

a computer network that uses open protocols to standardize communication

Computer network

interconnected computing system that is capable of sending or receiving data

Computing system

group of computing devices and programs working together for a common purpose

Computing device

a physical object that can run a program such as computers, tablets, cell phones, and smart sensors

The World Wide Web

a system of linked pages, programs, and files that uses the internet

Router

computer that passes information from one network to another

ISPs (Internet Service Providers)

the companies who sell internet access to homes and institutions; computer connected to the internet and the connections among them don't belong to any one organization as different ISPs provide the internet to difference communities

Bandwidth

the maximum amount of data that can be sent in a fixed amount of time (for digital data it is measured in bits per second); higher the bandwidth the better because data travels more quickly

The cloud

data stored in the cloud means storing it somewhere on the internet, but you don't know where; the cloud service provider manages the actual storage location

A path

a sequence of directly connected computing devices that connect a sender to a reciever

Routing

the process of finding a path from sender to receiver

Scalability

the ability of the Internet to keep working as it grows

Redundancy

the inclusion of back-up elements in case one part fails

Fault tolerance

the ability of a system to work around problems

Protocol

a set of rules that specify the behavior of a system

IP Address

a unique number assigned to each device on a computer network

Packet

a small chunk of any kind of data and metadata that is passed through the internet as a data stream

Packet switching

the internet sends short bursts of information, not long continuous strings

What is TCP/IP

a pair of protocols that provide two levels of abstraction

IP (Internet Protocol)

lets your computer pretend it has a direct connection to another computer. the routers at every connection point on the internet run IP, which transmits packets from one IP address to another

TCP (Transmission Control Protcol)

lets your computer pretend it has a reliable connection to the other computer. The computers at the two endpoints of a communication run TCP, which guarantees the packets arrive successfully

Encryption

the process of encoding data to prevent unauthorized access

Decryption

the process of decoding data

Symmetric encryption

uses the same key for encryption and decryption (Ex: substitution ciphers)

Public key encryption

uses a public key for encryption and a private key for decryption. The sender uses the public key to encrypt the message, and receiver uses their private key to decrypt it

SSL/TLS

the standard used for cryptographically secured information transfer on the Internet.

Certificate authorities

organizations that issue digital certificates to verify who owns the encryption keys used for secured communications; instead of trusting the website is who they claim to be, you have to trust the certificate authority

Malware

software that was designed to harm or take partial control over your computer

Keylogging software

a kind of malware that records every key pressed by a user

Computer virus

a type of malware that spreads and infects other computers; viruses can attach themselves to legitimate programs

Antivirus or anti-malware software

software designed to scan your files and internet transmissions looking for malware

Firewall

a security system that controls the kinds of connections that can be made between a computer or network and the outside world

Phishing

a common security attack in which the victim is tricked into giving up personal information or downloading malware; attacker can then use your personal information to gain access to personal online resources

DoS (Denial of Service) attack

sending a lot of requests to a server at the same time to overload the server's network bandwidth; doesn't destroy data or collect passwords just makes it so the user of that server is denied service

DDoS (Distributed Denial of Service) attack

uses a virus to flood a server with many requests from many computers at once so that users of that server are denied server; the attacker first uses viruses and other malware to take control of many computer around the world and this network of computers is called a botnet; the attacker then launches a DoS attack from all of the victims' computers at the same time; DDoS makes it harder to determine who's at fault

Rogue access point

a wireless access point that gives access to a secure network without the authorization of the network administrator

Digital divide

refers to unequal access to computers and the internet based on poverty, racism, sexism, isolation in the countryside, age, and other factors; affects both individuals within a country and countries themselves

Citizen science

scientific research conducted in a whole or part by distributed individuals who contribute relevant data to research using their own computing devices

Crowdsourcing

general term for using the internet to get a lot of people to help solve a problem

Computing innovation

can be physical or non-physical software, or conceptual, but regardless of the form they must include a program as an integral part of their function