Flashcards: Introduction to Computer Science Period 1

Arithmetic Logic Unit - It combines multiple full adders and additional logic circuits to perform arithmetic and logical operations (AND, OR, XOR, etc.)

A code that represents what operation the ALU is to carry out, and which operands to use for it

The input(s) that the ALU is making a calculation with

A code that represents a message such as an error or important notice. Eg. an overflow error.

Controls the flow of data to and from the CPU and memory, it fetches instructions from memory, interprets opcode and determines what actions to carry out to process data.

They temporarily hold data which the CPU is using for processing. Eg. data register and address register

The number of transistors in a dense integrated circuit doubles about every two years

A collection of binary-coded instructions that a computer's CPU can execute

1,000

8,000,000

166

A set of rules that precisely defines a sequence of operations

You can't write a piece of code that tells you when another piece of code will stop or if it would stop at all without running said code

A mathematical model of a computing device. A mathematical computing machine.

Mathematical simplicity, intellectual robustness, and so we can understand programs and machines more broadly, as the model can apply to many different types of computers

Discrete finite automaton: No repeated options for one state, each option has one transition (line to another state) in each state

Yes

No

A finite set of characters or symbols, symbol ∑

All the possible strings you can make with an alphabet ∑, also called the universe

A finite sequence of characters/symbols (not a set)

L ⊆ ∑

A finite set of strings

L = {w ∈ {....} |(such that) w represents...}

There exists a DFA D such that L(D) = L (The DFA accepts/recognizes the language)

The language of all strings in ∑* that aren't in L

Non-deterministic finite automaton: More than one choice for the same option in one or more of the states. If there is at least 1 accepting path, the NFA accepts the input.

DFAs

No, dying is when there are no transitions for the next input, while rejecting an input is when after processing the input, the automaton ends in a rejecting state.

In NFAs, it is a transition that does not consume any characters from the input string, no matter how many times it is used

No

Personal Area Network, connects devices within 30 feet wirelessly, eg bluetooth

Wide Area Network, covers large areas such as cities and consists of smaller networks

Radio frequencies as a communication channel, sent and received by transceivers with antennas

Transmission capacity per unit of time, or rate

25Mbps

The structure and layout of network components

A direct connection between 2 endpoints that reserves the entire bandwidth for them. It's the type of connection that connects peripheral devices to a host.

Connects devices to a central device

Pros: if one wire fails, only one device fails

Cons: more expensive to set up and mantain

Each device is ideally connected to as many other devices as possible

All devices are connected to all other devices, the most expensive topology yet the most efficient one for information transfer.

All devices connect to a "bus", which then delivers the data to all other nodes, and the nodes then have to identify which data is meant for them. Inexpensive but one of the least efficient ones for information transfer.

Any point in a network

Data Terminal Equipment: stores or generates data

Data Communication Equipment: controls data speed, signal conversion, error checking, and routing

Directs data flow and controls packet switching

Converts signals so they can be transmitted through communication channels. Nowadays most home routers also act as modems.

It is a WAN and a network of networks where computers communicate to each other via the IP protocol

Domain name server, fetches the IP address of the domain name the user has entered, so the computer knows where to request data from

Application, Transport, Internet, Network

"The group of applications that let the user access the network", and where preferences such as whether to use SSL and encryption are defined. Data conversion through protocols such as HTML and CSS happen in this layer. Finally, session management (cookies) also occurs in this layer.

Simple Mail Transfer Protocol: Used for email transmission between mail servers

Responsible for end-to-end communication and data integrity (error checking, check-summing etc). Protocols such as UDP (user datagram protocol) or TCP (transmission control protocol) occur here

UDP is less reliable but faster (more suited towards things such as video streaming where high bandwidth is required without need for absolute accuracy), whereas TCP is more reliable but slower (suitable for transferring documents)

Information is separated into packets and sent separately, which are then reassembled at the destination. This ensures faster and more reliable transmission. TCP handles the package separation and reassembly and specifically it places more emphasis in checking whether the packages have been reassembled completely and accurately.

IP addresses, DNS

"An attack involving manipulating DNS records to redirect users toward a fraudulent, malicious website that may resemble the user's intended destination."

Physical connections between devices: communication channels

Application Programming Interfaces act as an intermediarybetween two applications (usually client and server), defining what operations can be performed on the server and how those operations can be executed, and the data format used for communication

4 and 16

Both. The devices on the same network see the private IP but the internet sees the public one.

Core Backbone - Owns underwater cables

Distribution - Owns infrastructure that connects to underwater cables

Connectivity - Connects users to said infrastructure

Users can get their connection from any of the three tiers

Unencrypted text

Hiding information inside other information

Encryption and decryption happen with the same key

Each party in the data transfer has two keys, a private one and a public one. Both keys are mathematically linked. They send the public one to the other party for them to encrypt the data they send, and only the private key can decrypt it. This is way more secure than symmetric encryption as you do not need to share any private keys at any point.

They use assymetric encryption: only the party who signs can do so, through a private key, and anyone can check if the signature is valid using the public key.

Your password passes through a mathematical function (which is easy to carry out but virtually impossible to undo) that turns it into random-looking information. This is what is ideally stored in a web server. Then, when you enter your password to log in, your password is not compared to anything on the server, but rather its hash is. This way your password never leaves your machine.

When a hacker gets you to type sensitive information into a fraudulent website

Try every known password as if they are trying all the words in a dictionary, generally starting with the most common passwords