Principles of Coding

Boolean Logic

Computer - transistors and circuits - components - 2 states - on/off. 2 states - represented - binary - 1 and 0. Boolean Logic - comparing different states using 3 main conditions would always output T and F values. Boolean

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Appreciation of Logic

Logical statements - evaluated as - T or F. Binary - 1 = T and 0 = F. Truth Table - a method of representing every single possible output based on inputs to a Boolean expression. Order of precedence: Not, And, Or

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NOT / NEGATION

Negation. These operators are implemented in hardware using logic gates. NOT takes an input and reverses it. Diagram. Describe truth tables. A = x or negation symbol A = x or A with bar on top = x

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AND - MULTIPLICATION / CONJUNCTION

Conjunction. Returns T if both conditions are T, else it returns F.Diagram. Describe truth table. A AND B = x or A upside down V B = x or A.B = x

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OR - ADDITION / DISJUNCTION

Disjunction. Returns T if either of the conditions are T. It will only return F if both conditions are F. Describe diagram. Truth Tables. A OR B = x or A V B = x or A + B = x

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HTML - Hypertext Markup Language

Front end development. Structure & content appearing on websites e.g. texts, videos and images. Layer HTML with CSS and Java Script - dynamic and visually compelling. Composed of elements - structure webpage and define its content.

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HTML Application

Structure of website + defines its content

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HTML Element

Unit of content in a HTML document formed by HTML tags, text or media it contains. HTML tag - element name < >. Opening tag < . Content - info between< />. Closing tag - used to end HTML element />.

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HTML Syntax

Doc declaration. Character declaration. Head. Title. Body. Headings. Div. Body close. Character declaration close.

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HTML Tags

Head - < /title>. Visible content - . Headings + SH to enlarge text. Text or blocks . Italics or bold . Ordered text (n). Unordered text (b). Images/Videos .

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HTML Linking To Other Web-pages

Add links to a webpage by adding anchor element and include text of the link inbetween opening and closing tags. Read out. Link open in a new window use target. Link to a relative page or same page.

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HTML Table

table. tr. td. th. colspan/rowspan attributes. thead. tbody. tfoot.

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Java Script - Key Characteristics & Application

Client-side tech/server-side. Dynamic, client-side scripts on web pages. Object-based scripting language.Can generate new functions within scripts. Form validation, web page effects and interactive content.

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Java Script - Key Characteristics & Application

Written inside HTML file. Invoke Java Script using different frameworks like React and Angular. Put Java Script in script tag. Each statement in Java Script ends with ;

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Java Script - Definitions

Function - A block of code designed to perform a particular task. Variable - item of data var name = "Jaya" . Object - Has properties and methods associated to it.

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Java Script - Array

List. Multiple values in a single variable. Write down example of array. Each item in an array is called an element. Arrays always start at 0. How to access an element from an array.

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Java Script - Function

A function is a block of code which performs a particular task. Use curly brackets. Give example of function.

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Java Script - Flow Control Statements - If Statement

Specifies a block of Java Script code to be executed if a condition is True. Give syntax.

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Java Script - Flow Control Statements - Else Statement

Specifies a block of Java Script code to be executed if a condition is False. Give syntax.

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Java Script Loops - For

Loops can execute a block of code a number of times. For loop requires 3 statements. Initial expression, condition & increment. Give example.

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Java Script Loops - While

Loops can execute a block of code a number of times. While loop has 3 statements. Initial expression, condition and increment. Give example.

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Java - Key Characteristics & Application

Software dev, mob app and large systems dev. Object based scripting language. Platform independent. Secure. Robust. Dynamic. Compiled - runs faster and ready to run. Syntax is different but concepts are similar to JS.

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Java Anatomy

Function - block of code which performs a particular task. Class - a container for one or more functions used to organise code. Method - a function which is part of a class. Statements end with ;

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Stack

A list of the major components which are needed to form a complete technology solution.

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LAMP Stack

Hosting websites and web applications.

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LAMP Stack

Linux - Operating system. Apache - Web server software. MySQL - database engine used to store a site's data. PHP - programming language used to generate dynamic webpages. Free and open source - popular.

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XAMPP Stack

Free and open source. Cross platform web server solution stack. Developed by Apache Friends.

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XAMPP

X - ideographic letter referring to cross platform. Apache - Web server software. MariaDB - formerly known as MySQL. PHP. PERL.

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PDF

Stands for Portable Document Format. File extension is .pdf .

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What is PDF used for?

Preservation of layout: images, fonts and format. Can't easily change content. Free to download via your web browser, don't need Adobe.

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Opening PDF Files

Web browser - directly open PDF file in a window of your browser. Adobe Acrobat Reader DC - read file. Form Fields - changes to PDF doc. PDF file size and compatibility - PDF Optimiser.

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HTML File

File with HTM or HTML file extension is a Hypertext Markup Language File. Text only files - they only contain text or text references to other external files. Video, CSS or JS. Browser decodes HTML file - correct content.

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GIF File

Graphics Interchange Format. File extension - .gif. Short, animated vid loops. Supports 256 colours - smaller than JPG due to this. Lossless compression. Limited transparency. No alpha transparency.

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PNG File

Portable Network Graphic. File extensions - .png. Illustrations, diagrams and app screenshots. Change colour of png file - fewer colours more it shrinks. Losless compression. Image saves on transparent background,

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JPG/JPEG File

Joint Photographic Experts Group. File Extension - .jpg or ,jpeg. Photos instead of graphics. Smaller file than PNG. Lossy compression. Faster image load time - better user exp. Saved on non transparent background.

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Use PNG over JPG when...

High quality image. Save and edit multiple times. Text in image as JPG will reduce quality. Transparent background.

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Lossless Compression - PNG and GIF

Removes redundant data but tells computer how much of that data was redundant and how to rebuild the image.

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Lossy Compression - JPG

Data is removed for good. Save/edit multiple times - more data is lost which reduces the quality of the image.

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Video - MPEG

Moving Picture Expert Group. File extension .mp4. Standard format for compressing digital audio and video files. Windows Media Player, iTunes, Quick Time and VLC Media Player.

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Audio - MP3

Created by Moving Picture Expert Group. File extension .mp3. Lossy compression.

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Widget

A way of accessing another social media platform via another website.

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Social Media Widget

Allows user to input profile URL. Shows icon on side bar to that social media platform. Opens up in separate browser window.

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What does API stand for?

Application Programming Interface

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What is an API Key?

A unique identifier used by a third party developer to verify that their code is a valid implementation based on the API developer's databse.

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What is an Application Programming Interface? API

A set of functions and procedures allowing the creation of applications that can access features/data of operating systems, application or service.

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Structure of an API Key

Value - identifies your application and requests.

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User of Service

You must be accepted as a user of service before retrieving your API key. Once assigned an API Key you can use API in your code.

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API Key - Part of Request to Service

When you call API in your program, the API Key will be part of the request you make to the service.

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Service

The service can then identify you and send you application data in response.

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Why are API Keys used?

Identification and Authorisation

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Other Features of API Keys

Validates that the person who's trying to access the API is allowed to do so. Security. Encrypted set of numbers and symbols.

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HTTP - Hypertext Transfer Protocol

Request-response protocol in client-server computing model. HTTP request message. Server - HTML/functions. Response message.

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HTTPS - Hypertext Transfer Protocol Secure

Protocol for transmitting a secure connection which is encrypted by TLS.

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Transport Layer Security and Secure Sockets Layer

Cryptographic tools. Connection - private/secure. API authentication. Connection - reliable. SSL is older version of TLS.

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Web Server

A program which delivers web pages using HTTP over the WW. Its purpose is to deliver web pages to clients using HTML, CSS and JS.

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Web Application

Software framework devoted to the effective execution of programs, scripts and routines to assist the creation of applications.

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Differences between Web Server and Web Application

Web Server - Static / HTTP and HTML. Web Application - Dynamic

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Host

Computer hardware/device which is connected to a comp network. IP address. Source of info, service and applications used by remote terminals.

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Server

Provides functionalities to other devices/programs. Services include data and resource sharing to multiple clients. Single server can access multiple clients.

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Differences between a Host and a Server

Host - internet and consumes resources. Server - Local area connection, Internet and shares resources.

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Relational Database

RD - a type of database. Uses structure which allows us to identify data in relation to another piece of data in a database. Usually organised in tables.

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Relational Database Management System

A program which allows you to create/update a RD. SQL language is used to access the database.

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Content Management System

Software application used to manage the creation and modification of digital content.

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Web Client

The client or user side of the web. The web browser in the user's device.

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Web Browser

Software program to present and explore the WWW.

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Web Application

Any comp program that performs a function using the web browser as their client. Client side scripts and server side scripts.

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SEO - How mark-up languages render hyperlinks

Anchor element

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SEO - How web crawlers work - What is a web crawler?

Gathers information from hundreds of billions of web pages and organises it into a Search Index.

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SEO - How web crawlers work - Web crawler process

Software - web crawler - discover publicly available web pages. Crawlers look at web pages and follow the links. They go from link to link and bring back data from those web pages to Google's servers.

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SEO - How web crawlers work - Search process

Crawling - examine content. Indexing - categorise content. Ranking - use to see which content is most useful to use.

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SEO - Display of Search Results

Paid Results (Ads). Knowledge Graph. People Also Ask. Organic Results.

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SEO - Display of Search Results (detail)

User - query - SE - SERP - paid/organic results. Paid results - how much advertisers are willing to pay for CTR. Paid results - Auction/bidding - max amount - CPC.

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SEO - Display of Search Results (detail)

Organic results - based on SE's algorithm - identify which pages indexed by web crawlers are useful, helpful and relevant. More relevant - higher in SERP. Algorithm is updated and refined.

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SEO - Factors which affect SEO

Content (relevant and high quality). Backlinks. Meta data. Speed (load). Mobile friendly - responsive design. Accessibility - screen readers. Keyword Optimisation.

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SEO - What is Meta Data

Key words/phrases which describe contents of page. Meta tags are embedded in code and help SE. Metat title + description appears on SERP and helps SE.

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Static Website

Fixed content and pages. HTML - structure and content of website + CSS for styling. Some user interactivity - client side Java Script.

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Dynamic Website

Pull in content from a database. Interactively respond to user inputs. Supplement HTML and CSS with server side programming in a language like Java Script, PERL or PHP.

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Static Website - Comparison

Cheaper/Simpler - only using HTML and CSS - dynamic needs scripting language. Faster loading - Content ready to go - Dynamic - code needs to be processed to decide what to show.

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Dynamic Website - Comparison

Customer user exp - Content can be dynamically generated based on user. CMS - static - change - Raw HTML - dynamic - CMS. More complex features - online store, forum or social media.

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What is a cookie?

Small piece of data that a server sends to a user's web browser.

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Process - Cookie

Browser may store cookies but doesn't have to - incognito and session clear cookies. When a browser does store cookies - it will be sent back to the server to help with the next HTTP request. Cookie helps server for next appropriate HTTP response.

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Cookie - 2 Main Purposes

Authentication - Identify when a user is logged in and which user it is. Personalsied Session Memory/History - Remember user input and session behaviour e.g. form data, buttons or item in shopping cart.

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W3C - World Wide Web Consortium

Created to help WWW achieve its full potential by developing standards to ensure long term growth. Develop standards for web - websites look and work similarly in all browsers.

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W3C Standards

HTML - content/structure - applied to web pages and web application. JS - uses web techs - Web APIs. Accessibility

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Internet Engineering Task Force - IETF

Est to make internet work better - high qual and relevant tech docs - influence those designing and managing web. Self organised community, D,O, R - discuss - work groups - vol standards for Internet.

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IETF Standards

TCP - Transmission Control Protocol - How data is transported and delivered around the web. IP - Internet Protocol - How devices on internet are identified - IP Address.

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Principles of Coding

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