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Computer Science > CS50 Understanding Technology > Flashcards

CS50 Understanding Technology Flashcards

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1
Q

What number system do computers use to represent info?

A

Binary

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2
Q

How do computers implement the binary number system to represent 0’s and 1’s

A

Using switches called transistors

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3
Q

A turned off transistor represents what number

A

0

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4
Q

A turned on transistor represents what number

A

1

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5
Q

How do computers map numbers to characters

A

Using ASCII or Unicode

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6
Q

What does ASCII stand for?

A

American Standard Code for Information Interchange

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7
Q

How many bits are in a byte?

A

1 byte = 8 bits

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8
Q

Why is Unicode preferred over ASCII?

A

It uses more bits so it can map to more characters

ASCII: 7bit

Unicode: 8bit, 16bit, or 32 bit

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9
Q

Why are more cores on a CPU better?

A

The more cores, the more tasks a CPU can do at once

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10
Q

What is hyper-threading?

A

A single core presenting itself as multiple cores to a computer’s operating system

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11
Q

What is a System on a Chip (SoaC)?

A

A CPU and more are all interconnected rather than attached to a motherboard (phones, tablets, game consoles, Raspberry Pi)

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12
Q

Fast access memory that only stores data when the power is on

A

RAM (Random Access Memory)

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13
Q

What does 1.94 GHz mean?

A

The CPU can perform 1.94 billon operations per second

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14
Q

Slower but permanent computer data storage

A

Hard disk drive (HDD)

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15
Q

How does a HDD work?

A

Magnetic particles are used to store data where north pole orientation represents 1 and south pole orientation represents 0.

Metal platters physically spin around while reading heads move back and forth reading data from the device.

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16
Q

How does a SSD differ compared to an HDD?

A

An SSD uses electronic flash memory and has no moving parts.

SSDs are faster than HDDs but may not last as long.

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17
Q

A tiny amount of memory (bytes) where numbers are stored for operations

A

Registers

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18
Q

Memory built into the motherboard

A

L1, L2, L3 cache

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19
Q

Wireless internet

A

Wifi

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20
Q

Allows devices such as wireless keyboards and headphones to connect to your computer with a limited range

A

Bluetooth

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21
Q

ISP

A

Internet Service Provider

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22
Q

How to do home networks connect to the internet via the telephone infrastructure?

A

Cable modem, DSL modem, or FIOS device

This device could have built in wireless connectivity for your devices or you may need an additional home router

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23
Q

IP

A

Internet Protocol

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24
Q

.#.#.

What numbers are used in an IPv4 address?

A

Four numbers separated by dots of the values 0-255

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25
Q

What does an internet protocol address do?

A

They uniquely identify devices connected to the internet

Any device connected to the internet has an IP address

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26
Q

DHCP

A

Dynamic Host Configuration Protocol

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27
Q

How does your home computer get an IP address?

A

It’s assigned by your ISP using DHCP

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28
Q

What does DHCP do?

A

DHCP is Software that ISPs provide to allow your router to request an IP address

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29
Q

How do devices on your home network get an IP address?

A

The home router supports DHCP and assigns IP addresses to your devices

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30
Q

DNS

A

Domain Name Service

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31
Q

What does DNS do?

A

It converts domain names into IP addresses

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32
Q

How do computers communicate over a network?

A

Packets of data in binary format

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33
Q

What happens if the ISP’s DNS server doesn’t know a website’s IP address?

A

It will ask another DNS server.

There are root servers called “Authoritative Name Servers” that will know an IP if exists.

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34
Q

Why wouldn’t you send a large image in one packet?

A

Sending it in one packet could block internet traffic so it will be split up into smaller packets

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35
Q

TCP

A

Transmission Control Protocol

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36
Q

What is TCP/IP used for?

A

A set of conventions computers and servers follow to allow intercommunication

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37
Q

What does TCP do?

A

TCP ensures packets can get to their destination by allowing a computer to request a missing packet.

TCP standardized numbers that represent different services called ports

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38
Q

Port 80

A

HTTP

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39
Q

HTTP

A

hypertext transfer protocol

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40
Q

Port 443

A

HTTPS

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41
Q

Port 25

A

Email

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42
Q

What is a protocol?

A

A procedure or system of rules for doing something.

43
Q

UDP

A

User Datagram Protocol

44
Q

How do TCP and UDP differ?

A

UDP doesn’t guarantee delivery

45
Q

Why use UDP over TCP?

A

Use UDP when losing some packets is acceptable.

Use UDP when you don’t want buffering

Example: Video conferencing like Facetime

46
Q

Why is this IP format #.#.#.# limited?

A

Each number is 1 byte or 8 bits

4 bytes * 8 bits = 32 bits

2^32 = About 4 Billion IP addresses which is too limited for all the devices in the world today

47
Q

Why is IPv6 better than IPv4?

A

IPv6 uses 128 bits so it has many more available IP addresses

48
Q

Why do private IP addresses exist?

A

Because your device is not a server so the public doesn’t need to see it

Examples:

  1. # .#.
  2. 168.#.#
  3. 16.#.#
49
Q

What is a Subnet mask?

A

It’s used to determine if a device is on the same network

The subnet mask separates the IP address into the network and host addresses.

50
Q

Another name for a router?

A

Gateway

51
Q

What is a routers purpose?

A

To forward data in the direction of a destination via other routers

52
Q

What is the internet?

A

A network of networks each with their own routers

53
Q

Can packets take different paths across the internet?

A

Yes. Because of internet traffic the fastest path may change

54
Q

A program that sends packets to each router on a path to a destination, reporting the time it takes to reach that router

A

Traceroute

55
Q

RJ11

A

Phone jacks

56
Q

RJ45

A

Ethernet cables

57
Q

Coaxial cable

A

Cable tv

58
Q

Programs can synthesize the musical instruments for notes stored in these types of files

A

MIDI

59
Q

An early sound format using uncompressed data storage allowing high quality

A

WAV

60
Q

Audio format that uses compression to significantly reduce how many bits are necessary to store a song

A

MP3

It discards 0s and 1s that humans can’t necessarily hear

61
Q

What does lossy compression mean?

A

You lose quality in the compression process

62
Q

File format on iTunes

A

AAC

63
Q

How do streaming services like Spotify work?

A

They don’t transfer a file to you but rather stream bits of information to you

64
Q

The number of times per seconds we take a digital snapshot of what a person would hear

A

Sampling Frequency

65
Q

The number of bits used for individual snapshots of what a person would hear

A

Bit depth

66
Q

The number of bits necessary to store one second of music

A

Sampling frequency x Bit depth

67
Q

What is a graphic?

A

horizontal and vertical pixels

68
Q

RGB

A

Red Green Blue

69
Q

No color

A

Black

70
Q

All color

A

White

71
Q

The most common format for RGB values

A

Hexadecimal (base-16, contains 16 digits)

72
Q

How many bits are used to store a hexadecimal value?

A

4 bits

The largest number in 0-15 is 4 bits

73
Q

What is a single row in a graphic image?

A

A scan line

74
Q

Image type originally used by Windows

A

BMP (Bitmap)

75
Q

Image type that only supports 8-bit color and is usually used for low quality images but can also be animated

A

GIF

76
Q

Image type that uses 24-bit color and lossless compression

A

JPEG

77
Q

Image type that uses 24-bit color and is typically used for high quality images

A

PNG

78
Q

A bunch of images shown quickly in succession to create the illusion of motion

A

Video

79
Q

What are video file formats?

A

Containers that store multiple types of data.

A video track, audio track, a secondary audio track (for different languages), closed captions, etc.

80
Q

Video file format mostly used on Windows

A

AVI

81
Q

Video file format often used to stream video or audio on the internet

A

MPEG-4 Part 14 or MP4 is a digital multimedia container format most commonly used to store video and audio, but it can also be used to store other data such as subtitles and still images.

Like most modern container formats, it allows streaming over the Internet.

82
Q

Video file format used on MacOS

A

Quicktime

83
Q

A device or computer program which encodes or decodes a data stream or signal

A

Codec

84
Q

A spherical video image

A

3D video

85
Q

Data that tells programs, applications, and browsers how to display the image

A

Metadata

86
Q

Keeping people away from things you don’t want them to see

A

Privacy

87
Q

What does it mean to delete a file off of a hard drive?

A

An operating system doesn’t actually delete it from the hard drive it only forgets that the file exists.

88
Q

Little values a web server puts on a user’s browser

A

Cookies

89
Q

What are cookies used for?

A

They are used to remember if a user has visited a website before.

90
Q

What can happen if a hacker could obtains a cookie?

A

A session hijacking attack.

91
Q

What happens if you clear browser history and cookies?

A

Your history will be wiped clean and websites will forget you visited.

92
Q

How are session hijacking attacks prevented from wireless intercept?

A

Encryption scrambles the session cookie.

93
Q

What does Incognito Mode do?

A

Browser history is automatically removed.

94
Q

How many possible combinations for a 4 digit password with the values 0-9?

A

10 x 10 x 10 x 10 = 10,000 possible combinations

0000-9999

95
Q

Why will you will have to wait for an amount of time if you have entered a bad passcode?

A

It slows down the process of someone guessing.

96
Q

Software that stores on your phone or hard drive all usernames and passwords in an encrypted way

A

A password manager.

97
Q

A device that displays a unique value that is synced with a server used for 2FA

A

An RSA device

98
Q

Why is public WiFi sometimes dangerous?

A

Everything you do on http sites can be seen, but https or secure websites will still be private.

99
Q

A server that allows you to establish an encrypted connection to communicate for you.

A

A VPN (Virtual Private Network)

100
Q

Why can using a VPN can slow down speed?

A

Because we are encrypting data through an algorithm.

101
Q

Software that helps prevent people from accessing your computer

A

A firewall

102
Q

Cryptography using two keys, one public and one private

A

Public Key Cryptography

103
Q

An attack where an adversary sends a somewhat official-looking email

A

Phishing

104
Q

Malicious software

A

Malware

Computer Science (1 decks)

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