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computing revision (ISDD (Databases (Field types (Number, Graphic, Text,…

- - - - Number
      - Graphic
      - Text
      - Date
      - Time
      - Calculated
      - Boolean
      - Link
    - - A flat file database can be useful when only storing a small amount of records
      - Data can be duplicated
      - Because of duplication of data there's an increased chance of human error when typing in the same data
    - - Record - the set of information on one single subject (e.g. a student or individual from a school or university)
      - Field - is each individual heading for the information in each record (e.g. date of birth or name)
      - File - the whole set of data in a database
    - - Tables are linked to prevent duplication of data within a row of a table
      - Complex queries can be carried out on multiple tables
      - Easier to maintain security
      - Easier to change or update the data
    - - Range check
      - Restricted choice
      - Length check
      - Unique check
      - Presence check
    - - Simple search - A simple search involves searching on one field.
      - Complex Search - a complex search involves searching on two or more fields.
    - - Primary Key - every single record that is in the primary key is called something unique to identify someone or something specific
      - Foreign key - is used to link tables together and create a relationship between them. It is a field in one table that is linked to the primary key in another table
  - - - Internal - a hyperlink to another page on the same web domain
      - External - a hyperlink to page outside that web domain
      - URL - uniform resource locator, also known as web address is normally at the top of the web browser (e.g. www.amazon.co.uk)
    - - Server - is the part that tells you which server the web page is stored on (e.g. www.facebook)
      - Organisation - this is the part that indicates which organisation the web page is made for
        
        .co.uk would be for a company in the UK
        
        .sch would be a school
        
        .org would be a charity
        
        .gov would be a government organisation
      - Protocol - for example HTTP or sometimes FTP
    - - Absolute - specifies exactly on which server the web page is stored and directs you to that server and they always include the domain name of the website, including http://www
      - Relative - link you to a page on the same website (internal links). (e.g. courses/national5/notes.html)
  - - - Windows 7 interface is designed for use by mouse and keyboard
      - Windows 8 interface is designed for use by touch but can also be used by mouse and keyboard. It has tiles on the interface known as live tiles which lets you see information at a glance
  - - - Embed graphic in HTML - <img src="ben_nevis.jpg" alt="Mountain" style="width:300px;height:200px;">
      - Document tag - The <!DOCTYPE> declaration must be the very first thing in your HTML document before the <html>. It is an instruction to the web browser about what version of HTML the page is written in
      - Hyperlink in HTML - <a href="http://www.google.com">Click here to visit Google.com</a>
    - - JavaScript is the action and movement if you think about it as a person
      - HTML is the skeleton if you think about it as a person
  - - - Hardware - a keyboard is needed to type text, a mouse is needed to highlight or move large chunks of text and a monitor projector is needed to see what you're doing
      - TXT (Plain text file) -Standard text document that contains unformatted text is recognized by any text editing or word processing program and can be processed by most other software programs
      - RTF (Rich text format file) - it may include several types of text formatting, such as bold, italics, different fonts and font sizes, custom tab settings, etc. Can also support images saved within the text file. Recognized by most text editing or word processing programs and can also be processed by most other software programs
    - - WAV (Wave audio file) - is used for storing waveform data. It also allows audio recordings to be saved with different sampling rates and bitrates. Saved in the standard format for cd audio
      - MP3 - is a digital audio compression format that can reduce an original sound file to ten to fifteen times smaller than the parent file. The small file that is produced is easy and quick to download and is perfect for web use. Need an MP3 player to listen to the files
      - Hardware - a microphone to record sound, a cd/dvd drive or a usb/hard disk for music files, a sound card is a peripheral device that lets the computer to input, process, and deliver sound, speakers to turn electrical singals into sound
      - Sampling rate - the higher the sampling rate the better the quality which means the greater the file size
    - - JPEG (JOINT PHOTOGRAPHIC EXPERTS GROUP)- Mainly used on the web to reduce size of image and lessen download time. It uses compression to reduce file sizes, which leads to the loss of some of original data. It supports full colour. Capable of showing images containing over 16 million colours
      - GIF (GRAPHICS INTERCHANGE FORMAT) - Mainly used on web for images with sharp content such as logos, screenshots or basic animations. Capable of showing images containing 256 colours . Not suitable for photos
      - Hardware - digital camera, web cam, scanner
      - PNG (PORTABLE NETWORK GRAPHIC) - Created as a replacement for GIF on the web. It produces smaller file sizes than GIF images but is capable of showing images containing over 16 million colours. Suitable for photos
      - SVG (SCALABLE VECTOR GRAPHICS) - is used to define vector-based graphics for the Web. SVG graphics do NOT lose any quality if they are zoomed or resized.
      - Graphic resolution - the size of the pixels which is usually measured in dots per inch (dpi). High-resolution graphics has a large number of small pixels. Low-resolution graphics has a small number of large pixels
      - Colour depth - the number of bits that are used to code the colour of each pixel is called the bit depth. An image with only 1 bit depth will only represent 2 colours (21) – Black and White. An image with 24 bit depth will be able to represent 16777216 colours (224).
        1 bit: 2 colours 2 bits: 4 colours 4 bits: 16 colours 8 bits: 256 colours 24 bits: 16777216 colours
      - Compression - used to reduce the file size. Two reason for file compression is less storage space is required for the compressed file or the compressed file can be sent or downloaded quicker on the internet
      - File size - if you increase the resolution and the colour depth of a graphic you increase the file size.
    - - MP4 - a 'lossy-compression' method which means a lot of the original data is thrown away. Only throw away data in such a way that you do not notice a drop in video quality
      - AVI (Audio video interleave) - format is created by Microsoft. Uses less compression than similar formats
      - Hardware - Digital video camera, web cam
      - Frame rate - Moving pictures need many frames to be shown in one second in order to produce the effect of motion. The unit of measurement used is the 'frame rate'. The higher the frame rate, the smoother the film will appear to be, but this will require increased storage
      - Window size- Digital video has to store lots of information about each frame. The smaller the window size, the less time is needed to draw all the pixels. Reducing the window size reduces the amount of data which reduces the file size
      - File size and video quality
        File size and quality of playback are affected by:
        • Frame rate
        • Window size
        As the frame rate or window size increases then so will the file size
      - Compression - For video to be delivered over the web the file needs to be compressed. Compression will reduce the video and audio file size to a better delivery size