AMAZING Comp Sci 1033 Lecture Notes.docx

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Western University
Computer Science
Computer Science 1033A/B
Vivi Tryphonopolous

Comp Sci 1033 Exam Notes What is multimedia? - Everything you can hear or see - Technical definition: Describes any application or technology that can be used to describe text, sound, images, video, animation Multimedia uses: - To inform - To educate - To entertain Who uses the internet? - Asia has the most people and uses the internet more but North America has a higher usage per capita (I wasn’t sure on terminology) Quick Facts - In what decade was the first permanent photograph ever taken? o Between 1820 and 1830 - When was the first motion picture ever recorded? o Between 1880 and 1890 - What was the first full length movie with synchronized dialogue (i.e. the first talkie)? o The Jazz Singer - What was one of the first full length movies to use colour? o The Wizard Of Oz - What was the name of the predecessor to the Internet? o Arpanet, which was invented in 1969. Packet switching. Objection was to build a network where researchers could share information across the country. - Who invented the World Wide Web? o Tim Berners-Lee - What was the very first graphical browser for the World Wide Web? o Mosaic - What was the first band to give a concert over the internet? o Rolling stones - What was the first full length film that was completely computer generated? o Toy story - What application revolutionized the music industry in 1999? o Napster - When did digital cameras become fairly accessible to the public? o 1996 History Check 1969 – Arpanet 1991 – World Wide Web debuts thanks to Tim Berners-Lee 1992 – MS Window 3.1 is released 1992 – HTML debuts 1993 – first graphic browser is born, called Mosaic 2009- Multimedia continues to grow into more than a 20% increase every year Text Attributes - Font type: Ariel, Times, Comic - Style: Regular, Bold, Italic - Kerning: Space between ch arac t er rs o Measured in “em” negative, 0, positive - Leading: vertical Space between lines of text o Measured in pts also negative, 0 , positive - Size: pts vs. Pixels: 8 pt, 8 px script - Special effects: underline, shadow, super , subscript Font Types Serif [ E ] Sans Serif [ E ] - Tails - No tails - Script - Block oriented - Body Paragraphs - Headings, titles Pixels vs Points - Pixel sizes are smaller than points - Pixels should be used when designing for websites to avoid surprising size changes on other computers Pixel Points - The smallest discrete - A linear unit measuring size of text component of an image on a - Points are a print unit of measure (word monitor processing) - A measurement for text and - 1 pt = 1/72 inch images on the web - That is why 72 pt is always 1” Text colour - Hexadecimal code o Represented as number of six digits o Made up of decimals (0-9) and letters (A-F) o Represents RRGGBB Good Webpage Design - CRAP - Contrast - Alignment - Proximity - Repetition Graphics - Why rely on graphics? o Information o Explanations o Entertainment o Visual appeal Digitization - The process of translating pieces of information (text, images, sound, video...) into a binary measurement system Number Systems - Binary (2 Binary digits/Bits) o 1 bit is 2 =2 values (0,1) 2 o 2 bit is32 =4 values (00,01,11,10) o 3bit is 2 =8 values (000,001,011, 010, 011, 100,110, 111) o Etc... o Note: the exponent is the number of bits - Octal (8 digits) - Decimal (10 digits) - Hexadecimal (16 digits) What is an image? - Represented y a grid of squares called pixels. - Arranged in columns and rows - Each pixel is given a numeric value that corresponds to a colour How are colours coded? - Black and white uses 1 bit 8 - Grey levels: normal greyscale images have a bit colour depth of 256 shades of grey (2 ) Colour models Additive model (RGB) Subtractive Model (CMYK) - Primary colours (red, green, blue) light, are - Cyan, magenta, yellow ink are applied to a added to a black background to obtain white background and colours are colour shades subtracted - Used for web/computer images - Used when printing RGB Code - Each pixel is represented by 3 values <255, 255, 127> light yellow - Value ranges from 0-255 - 256 colour shades=2 bits o This means there are 256 shades of red, green, blue o Need 8 bit for true colour for each colour or 3 bytes (1 byte=8 bits) o 1 byte for red, 1 byte for green, 1 byte for blue <2 ,2 ,2 > o Therefore true colour is 2 about 16 million colours - Sometime we don’t need 16 million colours, then we use indexed colour (an index that maps to a group of colours we plan to use) o Our image might be 8 bits, so we can show 256 different colours o Called image bit depth Hexadecimal code - Notation is #RRGGBB - FF = 255 in RGB code Human eye - The human eye can detect about 10 million colours Types of Graphics - Bitmapped (also called raster graphics image) o images are made up of pixels and are resolution dependant o As you resize (not zoom) the squares become larger and edges jagged  Because, the computer adds new pixels and guesses their colour based on surrounding pixels. This is called interpolation o Quality decreases o File size increases o Shorter time needed to display it on the screen (advantage) o Distortion occurs when enlarged (disadvantage) o All images from scanners and digital cameras are bit mapped o Common formats: BMP, GIF, JPG, PNG, PICT, PCX, TIFF, PSD - Vector o Made up of scalable objects o Defined by mathematic equations o Consist of lines, curves, and shapes o No distortion o Most browsers won’t display them without a pug in o Can only be used with drawings no photos o Usually smaller file size than bitmapped o Common formats: AI, CDR, CMX, CGM, DXF AutoCAD, WMF, EPS - In Photoshop, “flatten Image” means it is changing your vector image to a bitmapped image Internet - Web server is the computer that delivers web pages - Client is the computer requesting to see/visit the web page - Many clients will visit one server Advantages of a web server - Connected: computer is always on and always connected to the internet - Since it is never turned off, your site is always available - Well maintained: the people running the servers will take care of security and computer maintenance issues Converting analog to digital - 2 step process - Step 1: sampling...How often do I take a sample to represent the thing (image, sound, text, video) - Step 2: many discrete values will be used to represent the thing Printing images on paper - Image must be printed at minimum 300 ppi - Thus if you had an image that was 3000 pixels by 1500 pixels, for the print quality to be good enough to the human eye, what size should you print it at? - 3000/300  10 inches by 1500/300  5 inches. So no larger than 10” by 5” Compression - Lossless o Compress the original bits and bytes into less bits and bytes without losing any original information o When we reopen the file the information is still there o One algorithm for gif compression: looks for patterns like 12345123451234512345 if 1 represents the pattern 12345 it can be compressed to 1111 - Lossy o When compression occurs some of the original information is lost o Selected portions of the image are discarded but the selected portions are lease noticed or missed o Cannot restore this info once compressed - Say we are compressing something that has 257 colours, but we only have 256. - Juxtaposing (place side by side) pixels of two colours to create the illusion that a third colour is present. - This process is dithering GIF JPG PNG-8 PNG-24 Best for Logos, cartoons, Photographs Logos cartoons Photographs and images drawings drawings with a need for transparency Type of compression Lossless Lossy Lossless Lossless Well supported in All All All Not in IE6 browsers Animation Yes No No No Dithering (most Yes No Yes No common form of reducing colour range) Interlacing Yes No Yes yes Shape of image Must be rectangular Note: allows for 48 bit colour (never necessary) Transparency One level None One colour Multiple levels - GIF: colour resolution vs. JPG Image quality Note: Recommended file size for graphics on the internet is no larger than about 100KB, otherwise it will add seconds to the download time Website development - Network: a group of interconnected computers (can be connected any way, wires, satellites wirelessly) The internet - A global system of interconnected computer networks that use the standardized internet protocol suite (TCP/IP) to serve billions of users worldwide. - The internet is hardware not software - The world wide web is software that runs on the internet - Idea was founded by ARPA (advanced research projects agency) of the US department of Defence (DoD) around 1969 - It is the opposite of your telephone where you get a direct line that only you and that person use o There is no direct line, is one communication line is broken another line is tried - How to connect to the internet? o ISP (internet service provider) by modem o Internet ready cable o Digital subscriber line (DSL) TCP - Take a large chunk of data like a webpage or email message and break it down into small packets - Sends these packets out on the internet o Packet: a small group of bytes consisting of:  Header (64 bytes) – consists of a destination and a source (where is came from and where it’s going)  Body (512 bytes) – actual message - At the receiving end, the packets are detected and lost packets are identified (error packets) because of network congestion, traffic requests that the packet is resent from source - Reassembles the packets back into webpage or email on the receiver machine - Protocol: rules for format and transmission of data IP - Like a GPS - Picks aroute for a packet, stopping at routers which pick the next best machine/network to send the package to. - It needs to be able to identify all the machines on the internet so each machine has its own IP adress - Consists of 4 numbers with dots between them from 0-255 ex - It is always 32 bits - Can be expressed as: Dotted Quad Binary 10000001 01100100 00010111 11110111 Hexadecimal 81 64 17 F7 Decimal 2,170,820,599 How to send a message (Packet Switching) - TCP breaks (for example) webpage into packets of bytes - TCP figures out IP address of where it wants to send packets (destination) - TCP figures out IP address of where packet is coming from (source) - Sends off each packet to first machine (IP address) on route *does not pre-plan route - Packet stops at first machine like a router then router sends it to next machine on the journey (IP address) and so on until it reaches its destination The opposite (circuit switching) one direct route to the source with no traffic all material together Domain names - In 1973 IP address became the standardized way to identify machines on the internet. - In 1984 university of Wisconsin came up with a name sever that maps a name to an IP address - In 1985 Domain Name System is established and the initial top level domain names are introduced ex: .com .net .org - In 1990 internet moved beyond government and universities and into commercial society - Up until 1995, you didn’t have to pay for domain names - 1995-1998 you paid NSF (national science foundation) 100 US for a 2 year registration for a domain name - 1998 domain name assignment is open to private companies to encourage competition How do domain names work? - A DNS (domain name system) maps the domain name to the correct IP address - In most cases there is a one to one mapping between an IP address and a domain name - Sometimes one IP address might map to more than one domain name and sometimes one domain name might map to more than one IP address o might map to and o and and … might all be web server machines for - Domain Names identify machines on the Internet, for example a web server machine. - Web server contains all the web pages for a company or individual - Web pages are stored on the web server machine in folders or directories - Web pages are just files, usually with the extension .htm, for example: myhomepage.html URL - Established by Tim Berners Lee in 1990 - Points a web page on the internet File spring.html is a webpage Hypertext Transfer file Domain Name Folder Protocol (http) Folder Rules on data is World Wide Web The name of its is a folder courses is a Indicates we are the site, points on the web exchanged between folder inside servers and browsers referring to the to the web server the its folder world wide web server machine machine Other examples: ftp://, news:// Break down the domain name: World Wide Web Third Level Domain Top Level Domain (TLD) Not a part of the Second Level Also a Sub domain Rules exist for what you can domain name! csd is a subdomain of Domain pick, only certain the domain combinations of letters have been established as allowable top level domains Sub Domains - Used to organize your web server just like folders, ex csd is a sub domain name of Rules for Domain Names - Each item between a dot is called a level - You can have a maximum of 127 levels - Each level can be up to 63 characters long except for the TLD - The entire domain name including sub domains cannot be more than 255 characters - Must use one of the approved TLD - Each level must consist of letters digits and hyphens - Each level cannot start or end with a hyphen - No spaces - Names are NOT case sensitive ISP (internet service provider - Provide user with o User account for accessing the internet o Email access o Web space to host your website - Some ISPs are o Rogers o Bell o Execulink o Western - What to look for in an ISP o Disk space – standard 5 GB – 10 GB o Bandwidth – the amount of traffic that is allowed to occur between your web site and the rest of the internet in a given time period o Web site speed o Database/programming language support – needs for dynamic website, interact with customers o Technical support – test this byu sending an email and seeing how long before they answer o Up time – must be up 99% plus guaranteed o FTP access – must be unlimited and unrestricted for easy maintenance o Web Statistics Summary – traffic on your website – easy access for easy maintenance o Scripts availability – counters, forms support o Web provider – reliabliy? How long? Popular? Note: htm and html are extensions of web pages - Other extentions are .shtml - .php .asp .cqi Web pages and web sites - A web site is a collection of related web pages stored in a folder. The folder may or may not contain a sub folder - The input we give a browser is code (page course) and the output we get is text/ images.... History: - In the late 1980s, Tim Berners Lee proposed a way of sharing research papers using the Internet and hypertext (immediate links to other documents) - In 1990 Berners Lee set the specifications for the HTML language and wrote a browser to read HTML files and output linkable papers - He proposed html tags o Example of some tags  , , , ,, o Tag always start with “” o Most tags come in twos: opening tag and a closing tag, for example This is the title of the web page - Originally we made html files (web pages) with simple text editors like Notepad 5 Types of Links - Links to pages within your site - Link to a different address - Link to an email - Link on an image (hotspot) - Link to a spot on a page (anchor or bookmark) Publishing your website ◦ Connect to internet if not already connected ◦ Start FTP program ◦ Enter the name of the web server (host name) ◦ Enter your username ◦ Enter your password ◦ Find the appropriate folder on the local machine (from folder) and the appropriate folder on the web server (to folder) ◦ Move the files from the local machine to the webs server ◦ Start IE or Firefox and check that the transfer worked correctly. ALWAYS CHECK!! Types of searches: Directories - Not automated - Real people decide how to organize it o Pick categories and hierarchies - Drill down into a category then into another subcategory then into another subcategory and so on until you get to a website - Webmaster submits his or her site to the directory and then humans decide whether or not it is “worthy” to be in the directory,
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