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Computer Science 008 > 3.3-5 > Flashcards

3.3-5 Flashcards

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1
Q

ISP (Internet Service Provider)

A

allows computers in a home or office to connect with the Internet. An ISP typically provides access via a cable line, a phone line, or satellite link line. Communicating over that line requires special electrical signals that are different from normal binary computer data.

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2
Q

modulation

A

A process that involves electrically combining with a different electronic signal capable of travelling over the ISP’s line in order to send a computer’s data which allows communication over that ISP abled line.

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3
Q

modem, short for “modulator/demodulator”

A

performs the required combining/uncombining of computer data and electrical signals over an ISP’s line. A modem typically connects to a computer using a communication protocol known as Ethernet over an Ethernet cable.

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4
Q

Ethernet

A

a communication protocol that helps a modem connect to a computer

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5
Q

router

A

commonly placed after a modem to route packets from the ISP’s line to the appropriate computer among many in a home/office, and sometimes routing directly between those computers. Routing between home/office computers is especially common for printing (a printer is a specialized computer), file transfers, and more.

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6
Q

Describe the process of home networking

A

A router sends packet towards a destination address. The modem modulates computer data and electrical signals to communicate to the ISP. The ISP provides a connection to the Internet. Multiple home computers can communicate with the ISP. An ISP delivers packets to the home, the modem demodulates, and the router send each packet to the appropriate computer. Packets can also be routed between computers within the home network, such as between a computer and a printer.

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7
Q

Wi-Fi router

A

uses wireless technology to communicate with computing devices over short distances of up to 66 feet (20 meters).

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8
Q

Wi-fi

A

referring to a wireless computer networking standard known as IEEE 802.11

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9
Q

What year was Wi-Fi introduced

A

1997

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10
Q

When did Wi-Fi’s availability and usage grow dramatically?

A

Around 2005

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11
Q

What is the advantage and disadvantage of modems that come with a built-in Wi-Fi router?

A

The advantage is easier setup and fewer devices/wires, but the disadvantage is that a user can’t change just one (as when wanting a faster Wi-Fi router).

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12
Q

hotspots

A

publicly accessible Wi-Fi networks provided by companies and cities either for free or for a price.

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13
Q

Describe the process of wired and wireless devices communicating over the home network.

A

Some devices are connected to the router wirelessly. Packets can be routed between computers within the home network by the router. Packets can also be routed to and from the Internet via the ISP.

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14
Q

How many Wi-Fi have been developed since the original 802.11 standard?

A

Five major versions (as of 2015), each improving the maximum speed of wireless data transfer.

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15
Q

Computers with older Wi-Fi versions will typically work with what version of a router?

A

a newer-version router, but may not obtain the new-version’s higher potential speed. Note: An ISP connection may limit the maximum speed to below that of a Wi-Fi router’s maximum.

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16
Q

What effect might an ISP connection have on the maxiumum speed on a computer?

A

may limit the maximum speed to below that of a Wi-Fi router’s maximum.

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17
Q

How many Mbps (megabits-per-second) is suitable for basic video streaming to one device?

A

About 5 Mbps

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18
Q

How many Mbps (megabits-per-second) is needed for high-quality video streaming to one device.

A

At least 20 Mbps

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19
Q

1997, 1999, 2002, 2009, and 2014 had what versions respectively and had how many Mbps?

A

802.11 = 2Mpbs, 802.11b = 11 Mpbs, 802.11g = 54Mpbs, 802.11n = 300Mpbs, 802.11ac = 1300 Mpbs

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20
Q

Which is the most recent version of the wireless computer networking standard?

A

802.11ac

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21
Q

802.11 versions are designed to be what?

A

backwards compatible with older versions. therefore an 802.11n roter can communicate with most Wi-Fi enabled computers and not just computer with 802.11n and/or 802.11ac (a newer faster version)

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22
Q

Describe the process of a system reboot.

A

Turn off one at a time starting from printer then router then modem (farther from wall to nearest). Turn on starting from modem (nearest to wall to farthest), being sure to wait about a minute for each to fully start.

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23
Q

When restoring power to network devices (turning them back on), which ordering is recommended?

A

Modem, router, PC

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24
Q

When did computer networks evolve?

A

The 1960s

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25
Evolved computer networks in the 1960s allow what?
omputers to communicate information with each other.
26
What is the most popular (but not the only) computer network today?
The Internet
27
What is FTP (file transfer protocol?
an early way for transferring files, like a word processing document or an image file, where a user would login to another computer, and then type commands to copy specific files among the computers.
28
A European researcher developed what in the early 1990s?
more convenient way for computers to communicate files, known as the web,
29
What three things does the web involve?
1. Text files, known as HTML files, containing links to other text files. 2. A program, known as a browser, for viewing HTML files. 3. A set of rules, known as the HTTP protocol, for transferring HTML files among computers.
30
HTML
hyper-text markup language (hyper-text means the text has links to other text)
31
HTTP
hyper-text transfer protocol
32
Who invented and when did they invent the web?
Tim Berners-Lee around 1989-1991
33
What is the difference between the Internet and the Web?
the Internet (the interconnection of computers communicating using a set of rules), and the Web (which is just one particular use of the Internet).
34
When was the first website published?
1991
35
When and how was Yahoo created?
by a pair of Stanford graduate students, who created a list of websites that they liked in 1994
36
web search
seeks web pages that best match user-typed words, like "rules of american football".
37
search engine
a website that does web searches.
38
When was Google created?
1998
39
default search engine
the engine a browser uses for searches done via the browser's search box or URL box, rather than by going to a search engine site like google.com. (ex. google chrome - google.com, internet explorer - microsoft's bing.com)
40
web crawler
a program that pre-visits web pages to build an index (of words pointing to specific pages)
41
dark web
the part of the World Wide Web that is only accessible by means of special software, allowing users and website operators to remain anonymous or untraceable.
42
page rank
a quality metric invented by Google's owners Larry Page and Sergey Brin. The values 0 to 10 determine a page's importance, reliability and authority on the web according to Google.
43
Using a minus before a word
excludes sites that have that word.
44
Including site: in a search
restricts searches to domains with that ending
45
Including filetype: in a search
limits results to files of that type.
46
ICANN (Internet Corporation for Assigned Names and Numbers)
a non-profit organization formed in 1998 and under contract from the U.S. Dept. of Commerce that manages Domain names and IP addresses
47
second-level domain
s commonly an organization's name as in Stanford.edu, or indicates the purpose of a website as in DoPython.org.
48
Third-level and further level domains
refer to sub-computer systems local to an organization, as in cs.stanford.edu where the cs is for Stanford's Computer Science department.
49
Cybersquatting
the practice of registering a domain name in the hopes of selling later for a profit, like registering coke.com before the Coca-Cola Company had done so
50
URL (Uniform Resource Locator)
the location of a file on the web, such as http://www.cdc.gov/alcohol/faqs.htm.
51
http part of the URL
refers to hyper-text transfer protocol used for communicating web pages
52
s in https
stands for secure
53
web browser
reads an HTML file and displays the page.
54
CSS (Cascading Style Sheets)
a language that can be used to style a web page via changes in colors, sizes, spacing, fonts, and more.
55
CSS color
can be a pre-defined name as in color:blue, or an rgb value as in color:rgb(50, 100, 255). rgb is short for red, green, blue; all colors can be formed by combining those three colors. Values range from 0 (none) to 255 (bright).
56
application (or just app
a program that a user runs to carry out a user task like listening to music or surfing the web.
57
operating system (or OS)
a program that implements the detailed interactions with hardware (among other things), presenting an application program with a more abstract interface like "Display '6' to the screen". a special program with various duties, such as interfacing with hardware (providing a more abstract view to applications), managing files and folders, and running multiple applications seemingly simultaneously (multitasking) for one or more users.
58
portability
a feature where the same application program can run without modification on different kinds of computers
59
filename extension
The extension informs users and applications of the file's type.such as myfile.pdf for a PDF file
60
PDF (Portable Document Format)
describes formatted text/graphics suitable for viewing and printing, independently of apps like a word processor, web browser, etc. PDF files are usually for viewing/printing only and are not edited by a user, but rather are produced by another app like a word processor.
61
multitasking OS
supports running multiple applications seemingly simultaneously, akin to a chef stirring the sauce a bit, then shaking a frying pan a bit, then stirring again, then shaking again, etc. To a user, multiple applications like a music player and a web browser appear to be running simultaneously, but in fact the OS is running a little bit of each application at a time, switching thousands of times per second.
62
multi-user OS
a multitasking OS that runs multiple users' applications, keeping each user's applications and files separate, and switching among applications fast enough (typically thousands of times per second) to give the user the illusion of being the only user on the computer.
63
os evolution
``` 1970-1980s = Early operating systems were text-based. Users would type commands. 1980-1990s = evolved to have simple graphical interfaces, including a mouse for pointing and clicking 1990-200s = The graphical interfaces improved dramatically, including rich colors, images, and functionality. 2000-2020s = Recent operating systems abandon keyboards and mice and instead have users do work by touching the screen and by using various multi-finger gestures. ```
64
cleaning up a drive
remove unneeded files, folders, and apps because as a computer gets used, new files, folders, and apps begin to fill the computer's drive (also called a disk).
65
memory leak
The longer the app runs, the more memory the app uses, even though the app doesn't really need the additional memory. Memory leaks are caused by certain bugs in the app, but apps aren't perfect so leaks are common. Leaks are especially noticeable in web browsers, which tend to be left running without quitting for long periods. Thus, a user may find that quitting and restarting an app, perhaps every few days, results in less memory usage and thus faster-running apps.
66
device drivers
The OS portions that interface with hardware. Ex: Upon connecting a new printer (hardware) with a computer, the OS may require installation of device driver software so that the OS can send proper print commands to the printer.
67
text file
only stores text without any formatting information, and typically has a filename extension like myfile.txt. Simple apps like Notepad (for Windows) or TextEdit (for Macs) can edit text files. (In contrast to formatted text i.e. Microsoft Word)
68
word processor
a computer application that can create, view, and edit such a file.
69
Data
a collection of facts and values
70
Information
processed data and gives meaning to the facts and values
71
Database
a collection of data organized to enable efficient information retrieval
72
SQL (Structured Query Language)
a popular language to run operations on databases. SQL became a standardized language in 1986 and is used in a number of DBMS' such as Oracle Database and Microsoft Access.
73
query
A query is a search in the database. Users can search for entries matching keywords, IDs, or other criteria.
74
analog
Audio is naturally an analog signal, meaning the signal changes continuously over time
75
Because computers can only store 0's and 1's, a computer records audio as what kind of signal?
digital signal, meaning as a series of numbers—digital means countable
76
LZ compression algorithm (named for creators Lempel and Ziv)
examines data for long repeating patterns such as phrases, and creates a dictionary entry for such patterns
77
Huffman encoding algorithm
measures the frequency of each data item like each letter, and gives the most frequent items a shorter bit encoding (like the letters "a" and "e"), with least frequent items getting a longer encoding (like letters "q" and "z").
78
Lossless compression
loses no information, so that decompression yields an identical file to the original. LZ and Huffman approaches are lossless.
79
Lossy compression
loses some information, so the decompressed file is close but not identical to the original. An example lossy compression approach is rounding. JPEG ex of lossy compression
80
quantization
A third compression approach is to round the numbers, So a pixel of 255 red, 64 green, and 231 blue (which is a shade of purple) may become 25, 6, and 23. Decompression might append a 5, yielding 255, 65, and 235, which is an unnoticeably different purple than the original.
81
H264
a more recent video compression approach than MPEG, intended to reduce bits further for fast transmission of video over networks. Video is a series of frames. Some frames are sent as an image (compressed), and others are sent just as the difference from other frames to achieve high compression.
82
MP3
Audio compression technique. An audio file is basically a series of numbers of sampled audio voltages. Audio compression may use techniques such as reducing how quickly audio voltages are sampled, or by using fewer bits to store the samples.
83
WAV
Uncompressed audio file. WAV files can be very large and are not typically used for portable devices or streaming.
84
Toubleshooting
a process of determining the cause of a computer problem, and ideally solving the problem. Two-step troubleshooting process for experienced troubleshooters is predict a probable cause of a problem and test the prediction

Computer Science 008 (4 decks)

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