Baseline questionnaire
5 Short answer questions.
These answers are rather fuller than those I expected in the questionnaire :-).
a) What tag is used to insert an image in an HTML page?
The <img … /> tag is used. It has a number of attributes, most important are
src URL the location of the image
alt the text to appear when the image is not displayed
width
height
b) What’s the difference between HTML and XHTML
XHTML is the version of HTML which conforms to the XML standard. This means that the fixed structure of the document must be adhered to <html><body>… </body></html>, all tags must have properly nested matching tags, all attribute values must be quoted (single or double) , and there is a defined set of attributes for each tags. Browsers accept any old HTML but if you use standard XHTML, then you can expect any browser to support it.
c) What’s special about a monospaced font?
The characters all occupy the same width. This makes it easy to calculate how much space a string will occupy.
d) Which image format would you choose for a chart – GIF. PNG or JPEG?
Charts are typically line drawings. If a lossy format like JPEG is used, the diagram will not be sharp so GIF or PNG should be used. File size will be smaller too.
e) What does the S in SVG stand for?
Scaleable Vector Graphics – it is a way of describing graphic images which may also animated. Because the image is defined by a set of vectors and areas, the quality of its appearance will depend on the display and rendering, not on the image itself. With a pixel-based GIF or PNG images, the resolution is built into the image. SVG is an XML application, so it can be generated by scripts.
f) What are regular expressions used for?
Regular expressions are typically used for pattern matching against a string, for example to check that data has been entered in the right format, (you could use one to check that a UWE module code has the right format) or to extract substrings for ill-structured data. Regular expressions are a technique available in Java, Perl and PHP.
g) What are the benefits of progressive download in video delivery?
2 benefits – viewing can start much sooner without waiting for the whole file, and video which is very long or may be real-time and hence endless can be streamed.
h) Can all visible colours be represented in RGB?
No they are not. The space of colors (gamut) possible with RGB lies within the space of all colors which are visible to the human (on average – eyesight obviously differs from person to person) . Greens are particularly under-represented - see Chapman and Chapman, Digital Multimedia
See http://en.wikipedia.org/wiki/International_Commission_on_Illumination for an explanation of the tongue-shaped area.
i) How is data on an HTML form passed to a script running on a server?
Data is passed either appended to the URL with name-value pairs (as the GET HTTP command) or as a separate file (as in the HTTP POST command). The server will strip this data off and make available to a script – PHP can just access the names as if they were local variables.
Here’s an example of data being passed as a string following the ‘?’ comprising name=value pairs separated by ‘&’ . Special characters in the string are replaced – here the space between RGB and gamut is replaced by a ‘+’
http://www.google.co.uk/search?hl=en&q=RGB+gamut&btnG=Google+Search&meta=
j) What is a Gantt chart used for?
A Gant chart shows usage by resource (person, facility.. ) over time on a project.
k) What is a histogram used for?
A histogram is used to display the frequency of occurrences
of grouped values –for example the age of people in the
l) What is the difference between a false positive and a false negative?
These are terms from statistical testing which apply to any selection situation. Suppose you have invented a test for Avian Flu. You hope that it will always test positive for every on who has it and negative for everyone who does not. But all tests make mistakes – of two kinds – it might report positive even if you don’t have avian flu (False Positive) or report negative although you do have it (False negative). Designing a test mist take the respective costs of these two errors into account. Its not just tests for diseases – the same idea covers tests for a spelling error, for whether an email is spam, for whether a student is good enough to pass a module, for whether a passenger is a terrorist or not.
m) What program would you use to show the HEX values of bytes in a file?
There are a number of file editors which will allow you to view and edit a file at bit level. Typically they would display the file in hexadecimal characters, so that a byte (octet) of 8 bits would be represented by two hex characters – e.g. A9 for 10x16 + 9 = 69 decimal. The Unix command od (octal display) is one way to view a file but there an a number of free HEX editors around. You should have one in your toolkit.