computer science test 1

&nbsp element

&nbsp special symbol forces a space to appear in the text the word &nbsp important &nbsp will have extra spacing around it

byte

-a collection of 8 bits- so can represent a range of 2^8 = 256 values large collections of bytes can be specified using prefixes: -kilobyte (KB): 2^10 bytes = 1,024 bytes (8,192 bits) -megabyte (MB): 2^20 bytes = 1,048,576 bytes (8,388,608 bits) -gigabyte (GB): 2^30 bytes = 1,073,741,824 bytes (8,589,934,592 bits) -terabyte (TB): 2^40 bytes = 1,099,511,627,776 bytes (8,796,093,022,208 bits)

cookies

-a cookie is a small file that can be stored and accessed by a web server -similar to caching, browsers reserve space (a cookie folder) on the user's computer -when the user visits a site, the web server is allowed to store a small amount of data in a cookie file (e.g., date and time of visit, items purchased) -when the user returns to that site, the web server can retrieve any cookies it previously stored -only the site that stored the cookie is able to retrieve it -cookies can improve the user's experience, but can also be intrusive; most browsers enable the user to control the use of cookies

internet society (ISOC)

-an international nonprofit organization (founded in 1992) -provides leadership in issues relating to the internet and serves as the organizational home of groups responsible for internet standards -It maintains and enforces standards, ensuring that all computers on the internet are able to communicate with each other -It also organizes committees that propose and approve new internet-related technologies and software

first search engines

-appeared in the mid 1990s -used software called web crawlers, or spiders, to surf the web, indexing pages -enabled users to search those indexed pages via search words or phrases -quality of early searches was not very good -the search for a word/phrase might return unrelated or unreliable pages

domain name servers

-are computers that store mappings between domain names IP addresses -translate the names into their corresponding IP addresses

bits

-are the building block of digital memory -are commonly represented as either 0 or 1 -by grouping bits together, large ranges of values can be represented

system modeling

-as computer memory and processing power has increased, it has become possible to model complex biological systems in software -can attempt to understand natural laws or behaviors by observing the model under varying conditions -can predict the effects of actions over long periods -can avoid infeasible, unethical, or costly experimentation

google search engine

-began in 1996 as a research project by Stanford grad students Larry Page and Sergey Brin -their goal was to create an easy-to-use search engine that produced high-quality results -founded Google Inc. in 1998 -google dominates the search market; performed 5.6 billion searches in 2019

internet protocol (IP)

-concerned with labeling the packets for delivery and controlling the packets' paths from sender to recipient -label packets with routes information (address) -the IP of the sender and receiver

transmission control protocol (TCP)

-controls the method by which messages are broken down into packets and then reassembled when they reach their final destination -break the message of the sender into packets (no longer than 1500 characters) -label packets with sequences (sequence of the messages) -reassemble the message to the receiver

World Wide Web

-created in 1990 -World Wide Web is software; consists of web pages, images, sound files, etc..., and the software that sores and retrieves those files -the web couldn't exist without the internet; the internet is the hardware that stores and executes the web software

hypertext transfer protocol (HTTP)

-defines how messages between browsers and servers are formatted -the prefix http:// in a URL specifies that the HTTP protocol is to be used in communicating with the server -the prefix https:// is similarly used for secure (encrypted) HTTP communications

hypertext

-documents with interlinked text and media -web pages can contain images and links to other pages

BODY section

-enclosed between <body> and </body> -contains the text that will appear on the page -only need one body

HEAD section

-enclosed between <head> and </head> -contains information that the browser uses to control the look of the page <head> <title> Title of the Page </title> </head>

TITLE section

-enclosed between <title> and </title> -title for the browser window <title> Title of the Page </title>

caching

-for efficiency reasons, browsers will sometimes cache pages/images -the browser reserves space (a cache folder) on the user's computer -to avoid redundant downloads, the browser will store a copy of a page/image in that reserved space (along with a time stamp) -the next time the page/image is requested, it will first check the cache -If a copy is found, it sends a conditional request to the server -essentially: "send this page/image only if it has been changed since the timestamp" -If the server copy has not changed, the server sends back a brief acknowledgement message and the browser uses the cached copy -catching still requires the browser to contact the server but only have to download the page if it has changed since last cached

packet-switching

-in a packet-switching network, messages to be sent over the network are first broken into small pieces known as packets -these packets are sent independently to their final destination 1. the message is broken into small packets, each labeled with a packet number 2. the packets travel independently across the network, perhaps arriving at the destination out of order 3. the packets are reassembled in the correct order to obtain the original message

Tim Berners-Lee

-invented the world wide web -researcher from 1984-1994 at the European laboratory for particle physics (CERN) -founded and serves as director of the World Wide Web consortium (W3C) -knighted by Queen Elizabeth in 2004 -CERN researchers were spread across Europe, but needed to collaborate -In 1989, Berners-Lee devised a system that would allow them to freely exchange data, regardless of location or computer type -his design integrated two key ideas: hypertext and the distributed nature of the internet

hyperlink

-is a connection to another Web page -a link is specified using ANCHOR tags <a> </a> -the text that appears within the tags is displayed as an underlined link -must have an HREF attribute that specifies the associated Web address (also known as URL) -an absolute (or external) address begins with http:// or https:// and is stored on a Web server -a relative or (internal) address is stored in the same folder as the referring page <a href="http://www.creighton.edu">Creighton University</a> <a href="personal.html">local page</a>

web browser

-is a program that accesses a web page, interprets its content, and displays the page -can be used to view pages stored on the same computer

web server

-is an internet-enabled computer that stores web pages and executes software for providing access to certain web document -It stores web pages and files (images, videos, ...) and sends them to browsers who request them -when you request a web page, the browser sends a request over the internet to the appropriate server -the server locates the specified page and sends it back to your computer

ARPANET

-precursor to the internet-became a reality in 1969 -It connected computers at four universities; UCLA, UCSB, SRI, and Utah -It employed dedicated cables, buried underground -the data transfer rate was 56,000 bits/sec, roughly the same as dial-up services today -the ARPANET demonstrated that researchers at different sites could communicate, share data, and run software remotely -was intended to connect only military installations and universities participating in government projects -needed to be resistant to attack or mechanical failure (distributed network and packet-switching) -by 1970, 18 sites were connected -most users had capability of 4 terminals per site -grew slowly and steadily through the 1970s -In 1980s, it exploded due to interest in email, newsgroups, remote login -by 1984, more than 1,000 sites were connected to the ARPANET

google's PageRank algorithm

-ranks pages based on their perceived value and trustworthiness -If a page is linked to by many other pages, that suggests that many people find its contents valuable and trustworthy -moreover, the more valued/trusted those linking pages are, the more impact their links will have

distributed network

-redundant connections provide alternate routes for messages, allowing them to circumvent failed machines or connections -will provide a communication network that is resistant to attack or mechanical failure

memory

-stores information to be processed as well as programs (instructions specifying the steps necessary to complete specific tasks) -modern computers store and process information as binary digits (bits) -memory capacity is usually specified in bytes

Central Processing Unit (CPU)

-the CPU is the "brains" of the computer, responsible for controlling its inner workings -carries out the instructions to process information-made of circuitry -despite its small size, the CPU is the most complex part of a computer (CPU circuitry can have 100s of millions of individual components) -the CPU works by repeatedly fetching a program instruction from memory and executing that instruction

internet of things (IoT)

-the growth of the internet has slowed if you only count traditional computers -since 2010, massive growth has occurred with non-traditional devices -e.g., mobile devices (phones, tablets, watches, Bluetooth accessories) -e.g., embedded devices (smart home appliances, automobile control systems) -IoT will make everything connected, e.g., smart cars, smartphones, smart homes, etc.

internet protocols

-the internet allows different types of computers from around the world to communicate because the computing community agreed upon common protocols (set of rules that describe how communication takes place) -the two central protocols that control internet communication are: 1. transmission control protocol (TCP) 2. internet protocol (IP)

bioinformatics

-the new field of bioinformatics bridges biology and computer science -the use of computer science techniques to solve biological problems

IP address

-the protocols rely on each computer having a unique identifier -an IP address is a number, written as a dotted sequence such as 147.134.2.84 -each computer is assigned an IP address by its internet service provider (ISP) -some ISPs (e.g., AOL, most colleges) maintain a pool of IP addresses and assign them dynamically to computers each time they connect

hypertext markup language (HTML)

-utilizes tags to markup page contents -these tags tell the browser how to display the contents -HTML5 is the current standard, supported by all browsers examples: -TITLE tags specify the title that appears in the browser tab -IMG tag specifies an image to be embedded in the page -A (for anchor) tag specifies a clickable hyperlink to another page

Von Neuman Architecture

-virtually all modern computers have the same underlying structure -named after computer pioneer, John von Neumann, who popularized the design in the early 1950's Identifies three essential components: 1. input/output devices 2. memory 3. central processing unit

impacts of computers on biology

1. computer technology is rapidly advancing the tools of scientific research 2. computer models are being used to study complex systems 3. computers are being used to store, process, and analyze large collections of biological data

advantages of packets

1. sending information in smaller units increases the efficient use of connections -large messages can't monopolize the connection -analogy: express lane at grocery store to limit waiting 2. transmitting packets independently allows the network to react to failures or network congestion -routers (special-purpose computers that direct the flow of messages) can recognize failures or congestion and reroute the packet around trouble areas -analogy: changing route if google maps reports traffic congestion 3. breaking the message into packets can improve reliability -since the packets are transmitted independently, it is likely that at least park of the message will arrive (even if some failures occur within the network) -software at the destination can recognize which packets are missing and request retransmission

A byte, which consists of 8 bits, can represent 256 (2^8) different values. How many different values can two bytes (16 bits) represent?

65,536

COMMENT element

<!-- demo1.html Lauren Goertz--> -nothing will happen if not included -a comment is ignored by the browser (it does not appear in the rendered page) -comments are used by the page developer to document page features

B element

<b> </b> specifies bold text here is some <b>bold text</b>

set multiple properties in the same STYLE attribute

<body style="background-color:gray; color:white"> entire page appears with gray background and white text </body>

BACKGROUND-COLOR property

<body style="background-color:lightgray"> entire page appears with light gray background </body>

BREAK element

<br> causes text to be displayed on a new line the last word will be on a different <br> line

HORIZONTAL-RULE element

<hr> draws a dividing line in the page

I element

<i> </i> specifies italicized text here is some <i>italicized text</i>

IMG tag

<img> images are embedded in a page using an IMG tag <Img src="http://compsciconcepts.com/images/DaveReed.jpg" alt="Dave Reed">

enclose a list item

<li> </li>

ordered list

<ol> </ol> <ol> <li> first item </li> <li> second item </li> <ol>

PARAGRAPH element

<p> </p> specifies text surrounded by blank lines <p> here is a paragraph </p>

SUB element

 specifies superscripted text (down) here is some _{superscripted text}

SUP element

 specifies superscripted text (up) here is some ^{superscripted text}

TABLE element

<table> </table> encapsulate the table data <tr> </tr> encapsulate a row within the table <td> </td> encapsulate table data within a row <table> <tr><td> name: </td><td> Lauren </td></tr> <tr><td> age: </td><td> 18 </td></tr> </table>

U element

<u> </u> specifies underlined text here is some <u>underlined text</u>

unordered list

<ul> </ul> <ul> <li> first item </li> <li> second item </li> </ul>

In most Web browsers, cookies are used to save local copies of downloaded pages and files in order to save time when they are accessed again. True or false?

False

In order to be classified as a "computer", a device must have a keyboard and display screen. True or false?

False

The World Wide Web was developed in the early 1970s, shortly after the development of the Internet. True or false?

False

Which of the following best describes the role of a domain name server?

It stores and distributes the IP addresses corresponding to domain names (e.g., www.creighton.edu)

Which of the following kinds of memory is volatile (i.e., requires a constant power supply to maintain its contents)?

RAM

BORDER style property

STYLE attributes can control how the table is displayed <table style="border:1px solid"> <tr><td style="border:1px solid"> name: </td> <td style="border:1px solid"> Lauren </td></tr> <tr><td style="border:1px solid"> age: </td> <td style="border:1px sold"> 18 </td></tr> </table> -table with solid borders <table style="border:5px solid; border-collapse:collapse"> <tr><td style="border:1px solid"> name: </td> <td style="border:1px solid"> Lauren </td></tr> <tr><td style="border:1px solid"> age: </td> <td style="border:1px sold"> 18 </td></tr> </table> -table with a thicker border

Which of the following best describes the role of a Web crawler, or spider?

They traverse the Web, cataloging Web pages for use by Web searches engines.

In a centralized computer network, the failure of a single machine or connection can isolate large portions of the network. True or false?

True

The ARPANET, the precursor to today's Internet, was funded primarily by the U.S. Department of Defense. True or false?

True

The protocol that defines how Web browsers and server communicate with each other is the HyperText Transfer Protocol (HTTP). True or false?

True

The three components that make up the von Neumann architecture are the CPU, memory and input/output devices. True or False?

True

There are currently more devices connected to the Internet (of Things) than there are people in the world. True or false?

True

list-style-type property

a STYLE attribute can be used to format the list elements with list-style-type property <ul style="list-style-type:lower-alpha"> -Items preceded by lowercase letters

output devices

allow the computer to display or broadcast its results examples: monitor, speaker, printer

input devices

allow the computer to receive data and instructions from external sources examples: keyboard, mouse, track pad, touch screen, microphone, scanner

input/output devices

allow the user to interact with the computer

Which of the following is NOT a task carried out by an operating system? a. control the CPU's operation, controlling how data and instructions are loaded from memory and accessed by the CPU b. manage the file system, organizing storage into files and directories c. control the circuitry of the CPU in order to execute program instructions d. provide a graphical user interface to make using the computer easier

c. control the circuitry of the CPU in order to execute program instructions

FONT-SIZE property

can be absolute (in pixels) or relative to the current size (as percentage) <span style="font-size:20px">this text appears 20 pixels tall</span> <p style="font-size:150%">this text appears 50% larger than normal</p>

STYLE attribute

can be used to set style properties for an element style="PROPERTY:VALUE"

TEXT-ALIGN property

can set the alignment of text elements <h2 style="text-align:center">centered heading</h2>

HEIGHT or WIDTH attribute

change the size of an image in a page <Img src="bluejay.gif" alt="Billy Bluejay" height=200> -will display the image with a height of 200 pixels, the width will automatically be adjusted to maintain the current aspect ratio <Img src="bluejay.gif" alt="Billy Bluejay" width=100> -will display the image with a width of 100 pixels, the height will automatically be adjusted to maintain the current aspect ratio

COLOR property

change the text color for an element <p style="color:red"> Here is some red text </p>

tools of biological research that integrate computer technology

confocal microscope -works by focusing a laser on a dyed sample and measuring the fluorescent light emitted -can be used to build up a 3-D model of a sample, stored on a computer DNA microarrays -measure the expression levels of genes

Which of the following statements about transmitting messages on the Internet is FALSE? a. Each computer on the Internet is assigned an IP address. b. The message is broken into packets using the Transmission Control Protocol (TCP). c. Packets are labeled with source and destination addresses using the Internet Protocol (IP). d. Each packet follows the same present path from the source computer to its destination. f. When the packets arrive at the destination, they are reassembled to yield the desired message.

d. Each packet follows the same present path from the source computer to its destination.

Which of the following claims about the Web is FALSE? a. Tim Berners-Lee invented the Web and developed the first Web browser and server software. b. A Web page is a text document that contains formatting information written in the Hypertext Markup Language (HTML) c. A Uniform Resource Locator (URL) specifies the address where a Web page can be found d. The most popular Web browser in the world today is Mozilla Firefox

d. the most popular Web browser in the world today is Mozilla Firefox

<html> </html>

encloses the entire html document

MARGIN-LEFT and MARGIN-RIGHT properties

indent the entire paragraph <p style="margin-left:10px">a paragraph with all lines indented</p>

TEXT-INDENT property

indents the first line of a paragraph <p style="text-indent:10px">a paragraph with the first line indented </p>

FONT-FAMILY property

must specify the font name and its family (as a backup) <p style="font-family:Helvetica, sans-serif"> this text appears in Helvetica </p>

TARGET attribute

opens the page in a new tab <a href="local.html" target="_blank">here is the link</a>

hardware

refers to the physical components of a computer system (e.g., monitor, keyboard, mouse, hard drive)

software

refers to the programs that execute on the computer (e.g., word processing program, web browser)

SPAN element

specifies a short span of text embedded in a paragraph <p> the word <span style="color:pink"> pink </span> is colored

ALT attribute

specifies alternate text to display if the image fails to load

SRC attribute

specifies the address (URL) of the image file the address can be absolute (external) or relative (internal) <Img src="bluejay.gif" alt="Billy Bluejay">

the Internet and the Web allow researchers to share data and publications

speeds the dissemination of information and the advancement of science e.g., PubMed, from the National Library of Medicine

<h2> ... </h2> encloses a...

sub-heading <h2>First Section</h2>

<!doctype html>

tells the browser that this is a Web page

operating system

the Operating System (OS) is a collection of programs that controls how the CPU, memory, and I/O devices work together -kernel: manages the CPU's operations, controls how data and instructions are loaded and executed by the CPU, coordinates other hardware components -file system: organizes and manages files and directories -graphical user interface (GUI): provides intuitive, visual elements for interacting with the computer (GUI's utilize windows, icons, menus, and pointers)

<h1> ... </h1> encloses a...

top-level heading <h1>Main Title</h1>

STYLE property and BODY element

when a STYLE property is assigned to the BODY element, it applies to all elements embedded in the page <body style="color:darkblue"> entire page appears in dark blue text </body>