file permissions
know what the three numbers after chmod represent
MIME
multipurpose internet mail extension; a standard for formatting files of different types, such as text, graphics, or audio, so they can be sent over the Internet and seen or played by a web browser or email application.
Web Safe color
The 216 colors that display consistently from computer to computer giving Web designers some control over their pages' appearance.
CSS Reset
A CSS Reset (or "Reset CSS") is a short, often compressed (minified) set of CSS rules that resets the styling of all HTML elements to a consistent baseline. In case you didn't know, every browser has its own default 'user agent' stylesheet, that it uses t
what does www stand for?
Worldwide Web
difference between internet and intranet
the Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but it is protected by a password and accessible only to authorized users.
Client Server Architecture
a computing model in which the server hosts, delivers and manages most of the resources and services to be consumed by the client. This type of architecture has one or more client computers connected to a central server over a network or internet connecti
LAMP stack
Linux, Apache, MySQL, PHP
Tim Berners-Lee
Invented the World Wide Web
how the web works
Clients (web browsers) send requests to web servers for web elements such as web pages and images. After the request is serviced by a server, the connection between client and server across the Internet is disconnected.
Client-side scripting
A program downloaded as part of a web page executed by the browser on the user's computer. (ex: js)
server side scripting
Also called back-end scripting; scripts are executed on the server before the web page is downloaded by a client. (e.g. if you log-in to an account, your input is sent to the server to be checked before downloading your account). These are the parts of th
cache server
A proxy server or application-level firewall that stores the most recently accessed information in its internal caches, minimizing the demand on internal servers.
proxy server
a server within an organization with a list of allowed and not allowed websites; filters requests from going to the internet
https
Hypertext Transfer Protocol Secure. Encrypts HTTP traffic with SSL or TLS using port 443.
TCP (Transmission Control Protocol)
provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
private IP and public IP
A public IP address is an IP address that can be accessed over the Internet. Like postal address used to deliver a postal mail to your home, a public IP address is the globally unique IP address assigned to a computing device. Private IP is used to assign
ARPANET
A defense-related computer network that was the precursor to the internet.
DARPA
Defense Advanced Research Projects Agency: An agency of the United States Department of Defense responsible for the development of new technology for use by the military.
router
A device that transfers data from one network to another in an intelligent way
DNS
the phonebook of the Internet. DNS translates domain names to IP addresses so browsers can load Internet resources.
DHCP
a network management protocol used on UDP/IP networks whereby a DHCP server dynamically assigns an IP address and other network configuration parameters to each device on a network so they can communicate with other IP networks
NIC
Network Interface Card; a computer hardware component that allows a computer to connect to a network. NICs may be used for both wired and wireless connections.
MAC adress
Media Access Control Address; a hardware identification number that uniquely identifies each device on a network.
UDP
User Datagram Protocol. Used instead of TCP when guaranteed delivery of each packet is not necessary. UDP uses a best-effort delivery mechanism.
TCP
Transmission Control Protocol - provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
What is a meta-search engine?
AKA an aggregator; a search tool that uses another search engine's data to produce its own results from the Internet. Metasearch engines take input from a user and simultaneously send out queries to third party search engines for results.
2-tier client/server architecture
...
3 tier client server architecture
...
Multi-Tier Client-Server Architecture
...
PKI
A public key infrastructure (PKI) is a set of roles, policies, and procedures needed to create, manage, distribute, use, store & revoke digital certificates and manage public-key encryption. The purpose of a PKI is to facilitate the secure electronic tran
certification authority (CA)
an entity that issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. This allows others (relying parties) to rely upon signatures or on assertions made about the private key tha
vulnerable points of an ecommerce website
three points of vulnerability
1. the client
2. the communication line
3. the server
what should be used to give the same style to elements scattered here and there?
class selector
DES
data encryption standard; a form of symmetric key encryption still used today
RSA
an algorithm used by modern computers to encrypt and decrypt messages. It is an asymmetric cryptographic algorithm.
digital certificate
a data file that identifies individuals or organizations online and is comparable to a digital signature
VPN (Virtual Private Network)
a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network
firewall
Hardware and software used to help prevent unauthorized users from accessing a person's data
two main ways that a firewall works
1. closing ports
2. packet inspection (can be deep packet inspection or header inspection)
how does anti virus software work?
the software keeps records of the digital signatures of viruses in order to identify malware
What is DoubleClick?
bought out by Google; sells ad serving services for displaying ads; gives a company information on the consumer to customize ads
how does Google work?
uses pagerank algorithm
1. sends webcrawler every day to examine metadata of webpages
2. indexes websitesbased on metadata
3.
what determines whether a script is client side or server side
the location where the program runs
characteristics of client side scripting
fast (because you don't have to wait for the data to come from the server)
can use client time and date
security risks
characteristics of server side scripting
heavier computations
more secure than client side scripting because programs do not run on client
dynamic/on demand
CentOS
CentOS and others like it (such as Scientific Linux) are largely compatible with RHEL and integrate some newer software, but do not offer the paid support that Red Hat does.
does PHP have a type char?
no. single characters are strings
what is VARCHAR?
a string that is not of fixed length
advantages of client side scripting
usability (faster UI)
efficiency (small changes can be made without server communication)
event-driven (can respond to user action)
error checking in forms
advantages of server side scripting
security (client cannot view source code)
compatibility (not subject to browser compatibility issues)
power (power requirement is moved to the server which saves client battery life)
is javascript interpreted or compiled?
interpreted
DOM
document object model; defines the logical structure of documents and the way a document is accessed and manipulated
different types of popup boxes in js
alert (displays alert)
confirm (returns T/F)
prompt (returns user input)
difference between null and undefined
null -> variable is declared but no value is assigned
undefined -> the variable has not been declared and doesn't exist
LAMP stack
Linux, Apache, MySQL, PHP
Web server
a web-server is software which listens for web page requests and serves web pages and media to clients upon request
web browser
fetches/displays documents from web servers
Client Server Architecture
clients make requests to the server and the server returns things
Open Source Software
Available to edit for free; no money could be made off changes
source code
A program in a high-level language before being compiled.
WWW vs the Internet
WWW -> a collection of web pages and media which can be viewed by a browser
Internet -> a network of networks; a collection of hardware and software which communicate with each other; encompasses the web and dark web
intranet
an enclosed network (self contained) which may or may not be connected to the internet
NAT
Network Address Translation. A service that translates public IP addresses to private and private IP addresses to public. It hides addresses on an internal network.
Client Side Programming
the program executes on the client's computer (ex: javascript)
server side programming
the program executes on the server's computer (ex: PHP)
javascript
small programs; used to make the client/ user interface look pretty and interact with the user
PHP
dynamically creates pages on the webs server; high level of computing; computations involving other servers
TCP
Transmission Control Protocol - provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
TCP/IP stack
Application
Transport
Network
Data Link
Physical
TCP/IP Stack - Application Layer
user side; ex: http, ssh, POP, ftp, SMTP
TCP/IP Stack - Transport Layer
End to end; ex: UDP, TCP
TCP/IP Stack - Network Layer
routing; ex: IP
TCP/IP Stack - Data Link Layer
ex: MAC, NIC
TCP/IP Stack - Physical Layer
bits on the wire
why have a stack?
because you can edit one layer, and the others will not be affected
protocol
a mutually agreed upon set of rules
ARPANET (Advanced Research Projects Agency Network)
A defense-related computer network that was the precursor to the internet.
Tim Berners-Lee
Inventor of the World Wide Web in 1980-ish and http in 1989
Key aspects of the internet
sub networks can stand on their own
computers can dynamically join (DHCP)
built on open standards
lack of centralized control
everyone can use (commonly available software)
DHCP
(Dynamic Host Configuration Protocol) to assign/lease dynamically IP addresses from a pool of IP aaddresses
IPv4 vs IPv6
IPv4: 32-bit number: 4 billion addresses; four sets of numbers marked off by periods
IPv6: 128-bit addresses, able to handle up to 1 quadrillion addresses; almost unlimited # of addresses
socket
IP + port
port 80
HTTP
port 443
HTTPS
port 25
port 22
SSH
HTTP Basic commands
GET
POST
PUT
HTTP command - GET
download
HTTP command - POST
send a web form response
HTTP command - PUT
upload
Web 1.0 vs Web 2.0
Web 1 -> one way communication
Web 2 -> two way (interactive)`
meta search engine
Sends request for information to several search engines simultaneously and compiles the results; does not manage databases as a regular search engine does
Cybersquatting
registering domain names in the hope of selling them later at a higher price
steps to making a website
1. get a domain name
2. find a web hosting service (this is where you site will reside)
3. Design (composed of analyse, organize, develop, implement, and maintain)
TLD server
Top Level Domain Server; a list of domain names with assigned IP addresses
Web hosting Service
a company with servers where you can store your web pages and media so that it can be accessible to everyone on the web
index.html
the universally accepted name for a web site's home page
Meta Tags
They are part of a web page's head section and describe a page's content; used by search engines for indexing
why should you resize images?
to maintain image quality; to ensure faster loading
why use relative path?
relative path allows the source files of a web site to be moved together to a different location, without reference paths breaking
Digitally enabled transactions
include all transactions mediated by digital technology
commercial transactions
involve the exchange of value across organizational or individual boundaries in return for products and services
e-commerce vs e-business
e-business is conducted within an organisation or firm
types of commerce
by nature of market relationship:
Business to Consumer (B2C)
Business to Business (B2B)
Consumer to Consumer (C2C)
by nature of technology used:
Peer to Peer (P2P; example: Bittorrent)
Mobile Commerce (M-commerce)
Systems Development Life Cycle (SDLC)
a methodology for understanding the business objectives of any system and designing an appropriate solution
Systems Development Life Cycle stages
planning (done on paper)
design (done on paper)
building (coding; about 50% of overall work)
testing (four main types)
implementation (+ maintenance; includes benchmarking)
Logical Design
The layout for the product and how it will work
(Part of the design phase of the SDLC in which all functional features of the system chosen for development in analysis are described independently of any computer platform)`
Physical Design
How the logical design is implemented
(The part of the design phase of the SDLC in which the logical specifications of the system from logical design are transformed into technology-specific details from which all programming and system construction can b
types of testing
unit
integration
system
acceptance
Unit testing
test individual units or pieces of code for a system
Integration Testing
After unit testing, integration testing is done to see that the modules communicate the necessary data between and among themselves and that all modules work together smoothly.
system testing
Testing the entire system as one entity to ensure that it is working properly
acceptance testing
provides the final certification that the system is ready to be used in a production setting
benchmarking
a process by which a company compares its performance with that of high-performing organizations
page generation
server response time
device based accelerators
efficient resource allocation
resource utilization thresholds
monitoring site performance
Page Delivery
content delivery networks
edge caching
bandwidth
page content
optimize html & images
site architecture
efficient page style
factors of website optimization
Page delivery, Page Generation, Page Content
Edge Caching
distributing content (e.g. videos and other bandwidth-hogging data) from a local web server to caching servers that are closer to the end user ( and nearer to the "edge")
How does HTTPS encrypt?
end to end encryption takes place in the browser;
HTTPS encrypts the entire comm channel using TLS.
what is httpd?
the d stands for Daemon which is a software program that runs in the background of a web server and waits (listens) for incoming server requests
hardware platform
in the context of e-commerce, this refers to all the underlying computing equipment that the system uses to achieve e-commerce functionality
what is the most important factor affecting the speed of a site?
customer demand
factors involved in demand include...
Number of simultaneous users in peak periods
Nature of customer requests (user profile)
Type of content (dynamic versus static Web pages)
Required security
Number of items in inventory
Number of page requests
Speed of legacy applications
Legacy
past/old hardware or software that is still in use
Scalability
Refers to how well a system can adapt to increased demands
what are the three aspects of scalability?
maintaining...
low latency
high throughput
high reliability
techniques to improve scalability of e-commerce web sites
Minimal size messages
Minimal number of messages
Minimal amount of computation
Local computation - move the computation to the data, instead of the data to the computation
Replication - Make copies of your computation and data, replicate databases and web
two ways to scale hardware
vertically and horizontally
vertical scalability
increasing the processing power of individual components
horizontal scalability
Employ multiple computers to share workload
8 most important factors in successful e-commerce designs
functionality
informational
ease of use
redundant navigation
ease of purchase
multi-browser functionality
simple graphics
legible text
http is stateless. What does this mean?
not remembering transaction history
cookies
small text files on the client's computer which can be set by the client or server
pros and cons of stateless servers
Chief benefit: Potential for replication
Improved performance: A sysadmin can fire up N copies of a website (on N machines) and any machine can serve each request.
Improved reliability: If a machine crashes, then another can be started up in its place, an
how do secure cookies work?
When user sends a valid username & password in request X, the server replies with a cookie containing a secret that the client couldn't possibly have guessed.
When user subsequently makes request Y, the browser sends along the cookie.
Since the client cou
session
state stored across requests
pros and cons of sessions
pros:
Stores information between requests
Much more secure than the simple cookie-based approach
A bad person would need to steal the random number (cookie) within 10 minutes of its creation
cons:
Requires your web server to have write-access to some sort
when to use cookies and when to use sessions
Use cookies when
You need to save a small amount of data between requests, and it doesn't need to be kept secret
Use sessions when
You need to save a larger amount of data between requests, or when the data needs to be secret
Dimensions of E-Commerce Security
integrity
nonrepudiation
authenticity
confidentiality
privacy
availability
Integrity
ability to ensure that information being displayed on a Web site or transmitted/received over the Internet has not been altered in any way by an unauthorized party
Nonrepudiation
ability to ensure that e-commerce participants do not deny (repudiate) online actions
Authenticity
ability to identify the identity of a person or entity with whom you are dealing on the Internet
Confidentiality
ability to ensure that messages and data are available only to those authorized to view them
Privacy
ability to control use of information a customer provides about himself or herself to merchant
Availability
ability to ensure that an e-commerce site continues to function as intended
DHCP
(Dynamic Host Configuration Protocol) A set of rules that allow network client computers to connect dynamically to a network. DHCP assigns IP addresses to computers
TCP
Transmission Control Protocol; Breaks files down into packets; provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.
What is HTML used for?
creating the structure and content of a web page
What is CSS used for?
The presentation and layout of a web page (to add font/size/pictures/etc.)
Why use html with a separate CSS file linked?
using only html would mean a long file and slow speeds
external CSS means one file can be used for many html pages
different forms of CSS
external style sheet
internal style sheet
in line CSS
HTML id attribute
...
HTML class attribute
...
<div> tag
<div> is an HTML tag used as the foundation of a CSS page layout to organize content on a web page by defining areas or sections
format of CSS
selector1 selector2{
properties
}
[here selector1 will only apply if selector2 is true]
CSS box model
a box that wraps around every HTML element, consists of (from the inside out) margins, borders, padding, and content.
float in CSS
sets the location of an element, for example you can use float to set an image to always be on the left of the page:
float: left;
position property in CSS
can be absolute or fixed
some div id tags that could be used on an html page
<header>
<nav>
<article>
<sidebar>
<footer>
Which are higher, download or upload rates?
download rates are always higher because more people download than upload
https://anselm.edu/academics.html
https = the protocol
anselm.edu = the host computer
academics.html = the web page
What is html?
Hypertext Markup Language; html describes the content and structure of information in a web page. html tags are interpreted by the web browser
what is CSS?
Cascading Style Sheets; CSS dictates the appearance of the content of a web page
2 tier CS architecture: Tier 1
client platform hosting a web browser
2 tier C-S architecture: Tier 2
server platform hosting all server components
advantage of 2 tier C-S architecture
inexpensive
disadvantages of 2 tier C-S architecture
inter-dependency of components
no redundancy
limited scalability
typical application of 2 tier C-S architecture
10 - 100 users
small company or organization
3-Tier C-S Architecture
separates server into application and data servers
advantages of 3 tier C-S architecture
improved performance from specialized hardware
decreased coupling of software components
improved scalability
disadvantage of 3 tier C-S architecture
no redundancy
typical application of 3 tier C-S architecture
100 - 1000 users
small business or regional organization
Multi-Tier Client-Server Architecture
has n number of tiers
is an expansion of the 3 tier architecture
advantages of multi-tier C-S architecture
decoupling of software components
flexibility to add or remove platforms in response to load
scalability
disadvantage of multi-tier C-S architecture
higher cost
application of multi-tier C-S architecture
1000+ users
large businesses or organizations
html for block quotes
<blockquote><p>text here</p></blockquote>
html for in line quote
<q>text here</q>
html for >
>
html for copyright symbol
©
metadata
gives information about the site
html for a table
<table>
<caption>title of table</caption>
<tr>
<td>first row first column</td>
<td>first row second column</td>
</tr>
<tr>
<td>second row first column</td>
<td>second row second column</td>
</tr>
</table>
what should you always do to make sure your code does not have errors?
upload it to a validator
what does CSS stand for?
Cascading Style Sheets
what are the benefits of using css?
one css file can dictate the style of multiple pages
faster browsing
uniformity between pages
css can be used in 3 ways:
<head>
inline
separate file
syntax for linking a css file to your html file
<head>
<link href="filename.css" type="text/css" rel="stylesheet"/>
</head>
what does pt mean in css?
One point is equal to 1/72 of an inch. Points are much like pixels, in that they are fixed-size units and cannot scale in size.
what does px mean in css?
One pixel is equal to one dot on the computer screen (the smallest division of your screen's resolution).
what does em mean in css?
An em is equal to the current font-size, for instance, if the font-size of the document is 12pt, 1em is equal to 12pt. Ems are scalable in nature, so 2em would equal 24pt, .5em would equal 6pt, etc.
when did the internet become open to commercial interests?
in the 1980's
what is the Internet Engineering Task Force (IETF)?
an open standards organization, which develops and promotes voluntary Internet standards, in particular the standards that comprise the Internet protocol suite
what is the Internet Corperation for Assigned Names and Numbers (ICANN)?
a nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces and numerical spaces of the Internet, ensuring the network's stable and secure operation
What is the World Wide Web Consortium?
The main international standards organization for the World Wide Web (abbreviated WWW or W3).
Founded and currently led by Tim Berners-Lee at MIT,[2] the consortium is made up of member organizations which maintain full-time staff for the purpose of worki
multiplexing
when multiple programs use the same IP address
what is a domain name server (DNS)?
a set of servers that map written names to IP addresses
what is a host file
a local cache of domain names and IP addresses
what is a Uniform Resource Locator (URL)?
an identifier for the location of a document on a website
what is Hypertext Transfer Protocol (http)?
the set of commands understood by a web server and sent from a browser
HTTP error code 200
OK
HTTP error code 301-303
page has moved
HTTP error code 403
you are forbidden to access this page
HTTP error code 404
page not found
HTTP error code 500
internal service error
what is SQL used for?
Used to store and retrieve data in relational databases.
<title>
placed within the head of the page
displayed in the web browser's title bar and when bookmarking the page
block vs inline html elements
block elements contain a margin of white space to separate them
inline elements are nested inside block elements and many can appear on the same line
which web technologies are used on the client side?
xhtml
css
javascript
which web technologies are used on the server side?
PHP
SQL
what is an ISP?
an internet service provider; a business or organization that provides you with an internet connection (comcast, verizon, Bellsouth)
what is DSL?
Digital Subscriber Line: A connection through a telephone company.
what are the basic tools for web development?
text editor (file creation)
browser (display)
file transfer program ( for uploading files to server)
what is MIME?
Multipurpose Internet Mail Extensions; a file's MIME type can often be inferred from the file extension
five step process for website design
analyse (why create this website?)
Organize (structure, content, layout)
Develop
Implement
Maintain
what kind of directory structure should be used for a website?
home page -> index.html
sub directories:
images
css
scripts
what are the main areas in which you will need to make decisions when building a website?
Human resources - Technical capabilities
Hardware
Software
Internet Service
Site design
32-bit IP address
four numbers with a dot between each. each in the range of 0-255
what is SSH?
SSH
is an encrypted and secure authentication protocol and uses Port 22.
What is FTP used for?
Access, edit and move files between devices on a network
...
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