COSC 1301 Exam 2

Video Formats/Player Apps

1. AVI- AVI (Audio Video Interleave) (file suffix .avi) is one of the oldest video formats, developed by Microsoft in 1992. Widely supported, but compression and video quality may not be as good as others. 2. Flash video- Flash video (file suffix .flv or .f4v) is a video format primarily designed to play in Adobe's Flash Player. Flash video is popular today in part due to wide use by YouTube. 3. WMV- WMV (Windows Media Video) is a video format developed by Microsoft for streaming video via the Internet. File sizes are typically small but quality may be poor. A special player may be needed for viewing on non-Windows devices. 4. MOV-MOV (Apple Quicktime Movie) is a video format developed by Apple for their Quicktime video player. The format is known for having high compression while maintaining quality. 5. MP4-MP4 is an international standard video format, since the early 2000's. MP4 is similar to the MOV format, known for having high compression while maintaining quality. MP4 is growing in popularity due to being made part of HTML5, meaning most modern web browsers can play MP4 video.

Types of Malware

1. Virus: A software virus is malware that spreads itself via attachment to a host file, like a biological virus attaches to a human. 2. Worm: A software worm is malware that spreads itself without using a host file. 3. Trojan: A software trojan (or trojan horse) is malware that a user installs believing the software to be legitimate, but the software actually has a malicious purpose. 4. Adware: Adware is malware that displays advertisements to the user, commonly in a web browser. 5. Spyware: Spyware is malware that collects information from a computer without the user's knowledge

Dictionary

A common approach to compressing data in a file is to create a custom dictionary for that data. In compression, a dictionary is a table of shorthand versions of longer data. Ex: Given a dictionary of 1: Department, 2: of, and 3: Redundancy (1, 2, and 3 are the shorthand items), then "1 2 3 1" is short for "Department of Redundancy Department". The compressed file will contain the dictionary itself plus the data in shorthand form, which combined is hopefully smaller than the original file. A typical text file might be compressed by 50% or more.

Word processor

A common computer application for creating formatted text Ex. Microsoft Word, Google Docs

Database

A database is a collection of data organized to enable efficient information retrieval. A company may use a database to gather information regarding current inventory or to forecast trends. A database may be on a local computer, but is commonly kept by a network server.

Database Management System (DBMS)

A database management system (DBMS) is an app that creates, maintains, and accesses database systems. Popular DBMS' include MySQL, Oracle Database, and Microsoft Access. Common database operations include: Adding new data Editing existing data Deleting data Querying the database for information. A query is a search in a database for data.

Font size

A font's size refers to the maximum height of any character. Font size is typically expressed in points

symmetric-key cryptography

A key is a number (or text string) used to encrypt or decrypt messages. In symmetric-key cryptography, the sender and receiver use the same key for encryption and decryption (symmetric refers to both sides being the same, in this case the sender and receiver keys both being the same). Ex: Given message "Hello", a simple encryption approach might shift each letter forward in the alphabet by some number of places. So a key of 2 would encrypt "Hello" to "Jgnnq" because J is 2 letters after H, g is 2 after e, etc. To decrypt, the receiver shifts each letter backward using the same key as the sender, in this case 2. Real cryptography uses sophisticated math techniques (not just letter shifting) and huge keys like 1099511627776 (not just 2).

hack

A malicious security breach done by unauthorized access is often called a hack. Hacks are the most common form of a breach. Other breaches may be caused by system glitches or by human error

Nigerian (419) Scam

A particular scam that builds a relationship with a person to help with a transaction, for which the person will supposedly receive a large payment.

Presentation App

A presentation app is a computer application used to create a slideshow of text and graphics, often with animation. A slideshow consists of a series of individual "slides". Work or school presentations are often accompanied by a slideshow to help the audience visualize information. Popular presentation apps include PowerPoint, KeyNote, Impress, and Google Slides (part of Google Docs) Presentation files are stored using special filename extensions such as .ppt, .pptx, .odp, or .key.

Relational Database

A relational database stores information in tables composed of rows and columns. Relational databases contain the following: Field (column): Basic unit of data stored Record (row): A group of related fields Primary key: A record's unique identifier Table: Collection of related data

Spreadsheet Application

A spreadsheet application is a common computer application for representing tables of data like text or numbers, for using formulas to calculate data from other data (like sums or averages), and for creating graphical charts from data. A spreadsheet contains cells organized into columns labeled A, B, ... and rows labeled 1, 2, ...; a spreadsheet user can type data in each cell.

Quantization

A third compression approach is to round the numbers, known as quantization. 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.

Video player app

A video player app reads a video file, decompresses, and displays frames at the appropriate rate. Most modern devices have a built-in video player app, such as Quicktime on Mac and iOS devices or Windows Media Player for Windows devices. A video player app can sometimes save a video file in different formats, such as MOV or MP4. A video player app usually doesn't support all video file types. Some users choose to download video player apps rather than use a built-in app, with numerous apps available in app stores. The free VLC app is a popular download for Mac and WIndows machines due to supporting nearly all common video file formats. Streaming means to play video directly from the Internet (such as from YouTube, Netflix, etc.), using a web browser or other app, without ever storing the video as a file on a device. Streamed video is viewable immediately but requires a good Internet connection. Stored video can be viewed with a weak Internet connection or when offline entirely, and sometimes may be higher-quality video. Purchased videos that are stored rather than streamed, such as when purchased from an app like iTunes, often include additional features known as digital rights management (DRM), to discourage unauthorized copying.

Internet scam

An Internet scam is a dishonest scheme or fraud using the Internet.

LZ Compression

An 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. Alternatively, a 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"). Many compression techniques combine LZ and Huffman algorithms.

Object-Oriented Database

An object-oriented database stores data as a collection of objects rather than tables. An object may consist of an ID, photo, and title, while another object may consist of a ID, video clip, and runtime.

Audio Basics

Audio, or sound, is the vibration of air molecules that human ears can detect. Audio is naturally an analog signal, meaning the signal changes continuously over time, like a flowing river. Because computers can only store 0's and 1's, a computer records audio as a digital signal, meaning as a series of numbers—digital means countable like a hand's fingers (fingers are also known as "digits", hence the word "digital"). A microphone converts vibrating air into an analog electrical voltage on a wire. An audio recording app may then rapidly "sample" that voltage (44,100 samples/second is common for music), using hardware called an analog-to-digital converter to convert each sample to a number, and storing the numbers in a file. An audio file is basically a series of numbers of sampled audio voltages, along with the sampling rate. An audio player app plays an audio file such that the audio can be heard, by sending numbers one at a time to a digital-to-analog converter, at the specified rate.

Arial Font

Characters in Arial font have smooth straight lines.

Compression

Compression reduces the size of a file. Ex: An image/photo file may be 4 megabytes before compression, but only 1 megabyte after.

A computer that has been hacked is said to be ___________.

Compromised.

Craigslist scam

Craigslist scam is an Internet scam where a seller receives an email from a buyer offering to buy an item. The buyer pays by check (or money order) and requests immediate shipment of the item. The seller deposits the check and sends the item, but in a few weeks the seller is notified of insufficient funds to cover the check. The seller has no means to get back the sent ite

Data Integrity

Data integrity refers to the accuracy of the data in the database.

Data

Data is a collection of facts and values. Ex: 23, 35, 48 is data.

EXIF/Metadata

EXIF is a common image format that include metadata. Metadata refers to extra information that describes data, like location information for image data, or author information for a word processing document.

Storing Audio

Each sampled audio value is stored using a fixed number of bits, known as bit depth, commonly 16 or 24 bits. Thus, an audio file can simply be a series of 0's and 1's, such as 0000000000000001 0000000000000010 0000000000000011 0000000000000011 etc. (representing numbers 1, 2, 3, 3). Of course, values typically span the range of possible values, such as 0011110111011110 or 1111000000000011. Audio files may be large. If each sample's number requires two bytes, the sampling rate is 44,100 samples/second, and a song is 3 minutes (180 sec), then a song's audio file would require about 180 sec * 44100 samples/sec * 2 bytes/sample = 16 MB (megabytes, or million bytes). Audio files are usually stored in compressed form to reduce file size. As such, a typical song file might only be about 4 MB. Common compressed audio file formats include mp3, AAC, and AIFF. A common uncompressed format (primarily for Microsoft Windows PCs) is the WAV format.

Encryption

Encryption scrambles plaintext into a cyphertext to prevent unauthorized users from accessing the information. Encryption is similar to writing a postcard using a secret code language, so that the information is not readable along the delivery route. While privacy and security are two different concepts, without security there is no privacy.

H264

H264 is a more recent video compression approach than MPEG, intended to reduce bits further for fast transmission of video over networks.

A computer with a virus is said to be ____________.

Infected

Information

Information is processed data and gives meaning to the facts and values. Ex: 35, 39, 40 are the number of sweaters sold by a store over the last three weeks.

JPEG

JPEG is a compression approach specifically for images. An image may consist of millions of pixels (short for "picture elements"), each pixel being a colored dot. A pixel may be 3 numbers (each a byte) indicating the amount of red, green, and blue. If an image has 4 million pixels, and each pixel requires 3 bytes, then a single uncompressed image is basically just a series of 12 million numbers (so 12 Mbytes). JPEG compresses the image using several techniques.

Lossless Compression

Lossless compression loses no information, so that decompression yields an identical file to the original. LZ and Huffman approaches are lossless.

Lossy Compression

Lossy compression loses some information, so the decompressed file is close but not identical to the original. An example lossy compression approach is rounding. Ex: Given an original file containing 255, 64, 231, the one's place can be dropped (a form of rounding), yielding 25, 6, 23. A decompressor, knowing of the rounding but not knowing what numbers were dropped, may append 5's, yielding 255, 65, and 235, which is close but not identical to the original. Lossy compression may be OK for data like images or audio where humans barely notice a quality difference, but is clearly not OK for precise data like text or bank account numbers since the meaning would change.

MPEG

MPEG is a compression approach specifically for video (a recent well-known version of MPEG is MP4). Video is a series of images called frames. If shown faster than about 15 frames per second (movies use 24, TVs use 30 or more), a human's vision system sees the images as a continuous video. The key idea of video compression is that successive frames differ only slightly, so a frame can be represented just as the difference from the previous frame. Ex: Frame 1 may be a full image, but Frame 2 may just be "Previous frame shifted left 2 pixels".

Malware

Malware (short for "malicious software") is undesired software that is typically installed without a user's knowledge and typically bad for the computer or user. A virus is one type of malware. The objective of malware includes doing damage, selling products, spying, and more.

Multidimensional Databases

Multidimensional databases store data in more than two dimensions. For example, a multidimensional database may contain multiple inventory tables with time as another dimension.

PDF (Portable Document Format)

PDF (portable document format) is a file format for storing documents (typically formatted text, images, and drawings) independently of any particular editing app like a word processor. A file that is useful across different applications, computers, or operating systems is said to be portable. PDF was originally created by a company called Adobe Systems and published in 1993; PDF was initially proprietary but as of 2008 became freely usable. Prior to PDF, a document created using one app like Microsoft Word, Adobe Illustrator, etc., could not be viewed on or printed from a computer that didn't have that same app. PDF viewing apps are common and usually free and thus included on nearly device today.

Audio Apps

Popular computing devices come with audio player apps, such as iTunes (comes with Macs, iPhones, iPads, and other Apple products), the Music app or Windows Media Player (for Microsoft Windows products), and a built-in music player for Android devices. Popular computing devices also come with apps for audio recording, such as Quicktime or Garage Band for Macs. Apps for editing audio files such as getting excerpts or mixing music are also available, such as Garage Band for Macs, or the free Audacity app.

Formatted text

Refers to features of a document like margins, text size, bold text, italicized text, colors, number of columns, etc.

SQL (Structured Query Language)

SQL (Structured Query Language) is 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. MySQL is a freely available database system that uses SQL. MySQL is a popular database for web apps.

Cryptographic Key

The cryptographic key is used by an algorithm to transform plaintext into ciphertext or ciphertext into plaintext. The stronger the encryption, the more computing resources are needed to break the encryption and access the user information.

Times New Roman Font

Times New Roman font uses varied line-widths, including tiny lines at the tips of characters known as serif.

Serif

Tiny lines at the tips of characters in a font

Phishing Scam

Tricking an Internet user into providing valuable information.

Troubleshooting

Troubleshooting is a process of determining the cause of a computer problem, and ideally solving the problem. Experienced troubleshooters may follow a methodical two-step troubleshooting process: Predict a probable cause of the problem, and Test the prediction by doing something to confirm or deny the prediction. If not confirmed, repeat step 1 (possibly with a different prediction).

Two-step verification

Two-step verification helps secure a user's account by requiring the user during sign in to enter a temporary code appearing on the user's mobile phone, which the user usually carries. A password thief who tries to sign in on a different computer will not know the code.

Validation

Validation ensures data is correctly entered as the data is added to the database. Periodic updates to the database ensure data is up-to-date.

Video

Video is a series of slightly-differing images shown fast enough to appear continuous to humans. Each image in video is known as a frame, and the number of frames per second (fps) is the frame rate. Digital video stores each image as rows and columns of colored dots, each dot known as a picture element or pixel. Standard video uses about 24 frames per second, and each image has 525 pixel rows (known as lines). Compared to standard video, high-definition video uses more frames per second (like 60) and more lines (like 1080), as well as wider lines.

Botnet

a large group of infected computers, controlled without the user's knowledge, to perform tasks such as sending spam.

Antivirus software

a program that looks for known viruses and strives to disable found viruses, by searching a hard drive, and/or by monitoring visited websites and downloaded files.

computer virus

a program that runs on a user's computer without permission, and spreads itself to other computers, often via email

Query

a search in a database for data

security hole/vulnerability

a weakness in the system that may lead to a security breach

Data Mining

data mining can analyze language usage, faces, locations, and other items to match a unique individual.

Cryptography

involves converting a message into an unreadable form (encryption), and converting that message back into a readable form (decryption), using secret conversion techniques that only the sender and intended receiver know.

Security Breach

is a case of unauthorized computer access. Ex. hack, human error, system glitches

Font

refers to particular text style features, such as the shape, thickness, and spacing of text characters. Commonly-used fonts include Arial, Times New Roman, and Courier New, illustrated below

denial of service (DoS) attack

requests simultaneously to one website, which overloads that site's web server, thus preventing legitimate requests from being handled (those requests are denied service). Infected computers are commonly used to carry out DoS attacks. Ex. Macy's and Kohl's

Text file

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.

Computer security

the prevention of unauthorized computer access, including viewing, changing, or destroying a computer or data

Cursor

typically a vertical blinking line, to indicate where a user's next-typed text will appear

Spam

unsolicited mass email, perhaps advertising prescription drugs for sale, or further spreading the virus. Spamming is illegal in many countries. If a spammer sent millions of emails from one computer, email companies might block that computer, and authorities might find the spammer. Instead, a spammer instructs thousands of infected computers to send the spam emails.

Courier New font

uses equal-width plain-looking characters that were common on manual typewriters several decades ago.

Public-key cryptography

uses two keys: A public key the sender uses to create encrypted messages, and a mathematically-related private key that the receiver can use to decrypt messages encrypted by that public key.