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Chapter 8 review. Are the following statements true or false? Explain why or why not.

a) Engineers tend to focus on machines, software engineers on user interfaces.
True, or it should be so. While software engineers need to consider features and performance just as other engineers do, they need to put more emphasis on usability. What is efficient or functional for machines is not necessarily so for people.

b) The function keys on most keyboards violate usable design, specifically visibility.
True, at least at first. Novice users do not easily understand what function and special control keys do. They are intended for "power' users, who learn some of their esoteric bindings (though rarely all of them).

c) The scroll bars on the sides of windows are effective because of real world mapping.
True. Up and down behavior mirrors expectations from other experiences, including experiences with other windows GUI programs.

d) Including alt tags in HTML are a good example of the feedback principle.
True. Alt tags give additional information about a graphic or what might happen if one clicks on it.

e) Clippy, Microsoft's help agent, is annoying to some users because it violates transparency.
True. Clippy has an annoying habit of covering the work space in a document and insisting that the user pay attention to it before continuing with his or her work.

f) Scroll bars are also effective because they can include more material than fits on a screen.
True, but misuse of scrolls bars can also violate the contiguity principle, putting text far away from what it is intended to explain.

g) The prototype for The Universal Machine (figure 8.3) succeeds at speaking the user's language.
False. The various buttons, such as "Out", "Hyperdrive", and "Probe" are cute in the spaceship, but do not label functions in familiar ways.
(That was actually the idea--we deliberately designed an interface that would be a bit unfamiliar, rather than ape Windows. But many users prefer that we stick with familiar vocabulary and real world mapping. There are tradeoffs here.)

h) It is a good idea (too often forgotten) to test a user interface by observing actual users.
True. Observing actual users try out a prototype early can help designer discover flaws in usability which may be crucial to a product failure or success.

i) JavaScript, Flash and other language run-time environments all assume an event-driven loop.
True. These environments are virtual machines that start up in a loop, waiting for and responding to user events, until the application exits. Developers write functions that reponds to user events.

j) When you look at a web page in a browser, you are viewing the source code of an HTML file.
True. HTML or HyperText Markup Language is a language for describing how to format information in a browser, and may include links to other documents.

k) Most markup tags come in pairs, for example and .
False. While most tags do come in pairs, such as and for old face, in an exception; there is not closing tag.

l) Many tags, such as <body> or , can take optional parameters.
True. For example, includes a parameter that centers the following paragraph.

m) Most browsers ignore extra white space in HTML files.
True. The first space between tokens appears in browser, but extra space is assumed just to be formatting the HTML code, not in the browser. To force extra space, you must insert   codes.

n) A URL is the name of a file.
False. A URL or Uniform Resource Locator is the address of a document on the web, which may include a host machine name, folders and possibly a file name. For example, "http://www.cse.lehigh.edu/~glennb/um" includes a host machine (www.cse.lehigh.edu) and folders on this machine (~glennb, where '~' or "tilda" binds to a user's web folder on this host, then folder um). In this case there is no mention of a file name, so "index.html" or "index.htm" is assumed.

o) An image map is how HTML supports the idea of "hot spots" in graphical images.
True. An image map segments a graphical image up into regions, each of which may contain a link to another web document.

p) JavaScript is a subset of the Java language that web browsers know how to interpret.
False. JavaScript has little to do with Java. When the browser vendor NetScape invented JavaScript, Java happened to "hot". It is true that most web browsers now know how to interpret JavaScript (or Jscript) and do so in order to achieve more dynamic behaviors.

q) An event handler embedded in an HTML form can invoke a JavaScript function.
True. For example, an event handler responding to a mouse rollover can invoke a JavaScript function that loads a different graphic, giving a rollover effect.

r) Document and Math are examples of objects built into JavaScript.
True. To access their features, one uses the dot notation associated with many object-oriented languages such as Java and C++.

s) JavaScript can do forms validation on both the client and server side of a web transaction.
False. Javascript can do validation in the client side browser only. Server side validation is usually done with other scripting languages, such as PERL.

t) Persistence of vision requires that animations have at least 30 frames per second.
False. Persistence of vision can be achieved with fewer frames (Flash defaults to 12 frames per second), though the effect may not be as smooth, especially for more complex animations or videos.

u) GIF and Flash animations both support automatic tweening.
False. Automatic tweening is a feature of Flash, not GIF89a.

v) JPG is a popular format for web graphics because of its codec.
True. JPG's compression/decompression algorithm is efficient are effective for photorealistic graphics.

w) Vector-based graphics tools typically "paint" pixels in an image.
False. They typically "draw" images following formulas for geometic objects such as lines, circles, rectangles, and polygons.

x) Unlike Dynamic HTML, Flash requires a plug-in to play movies in a browser.
True. Dynamic HTML is built into browsers that support HTML 4.0 or greater. The Flash plug-in comes pre-installed with many browsers, but if not, most Flash pages will prompt the user to install the most recent version of the plug-in.

y) You can use ActionScript to jump to specific pages on the web.
True. The "getURL" action will jump to another page.

z) It's a good idea to differentiate the states of a button in a Flash timeline.
True. With slightly different images in the "UP", "DOWN", "OVER" and "HIT" states, a button can provide visual feedback in response to different user actions, in keeping with Donald Norman's feedback principle.