In-person lab research used to be the only game in town, and as with most industry practices, its procedures were developed, refined, and standardized, and then became entrenched in the corporate R&D product development cycle. Practically everything gets tested in a lab nowadays: commercial Web sites, professional and consumer software, even video games (see Figure1-1).
Figure1-1.Brighton Universitys usability lab, from behind the traditional two-way mirror.
Part of the appeal of lab-based user research was that it provided a seemingly scientific basis for making decisions by using observational data, instead of someones error-prone gut instincts. Stakeholders appreciated the firm protocol and apparent reliability of properly managed lab research. Lots of user research practitioners continue to perform lab research just because its what people have been doing for a long time.
So now you have installed FreeBSD, and it successfully boots from the hard disk. If you’re new to FreeBSD, your first encounter with it can be rather puzzling. You probably didn’t expect to see the same things you know from other platforms, but you might not have expected what you see either:
FreeBSD (freebie.example.org) (ttyv0) login:
If you have installed xdm, you’ll at least get a graphical display, but it still asks you to log in and provide a password. Where do you go from here?
There isn’t space in this book to explain everything there is about working with FreeBSD, but in the following few chapters I’d like to make the transition easier for people who have prior experience with Microsoft platforms or with other flavours of UNIX. You can find a lot more information about these topics in UNIX for the Impatient, by Paul W.
Your Galaxy Tab is a powerful multimedia, productivity, and communications marvel. The first time you hold it in your hands, youll immediately want to put it through its paces, browsing the Web, downloading and trying out apps, playing games, watching videos, gathering news, checking your email, and more.
Thats as it should be: Your Galaxy Tab can do many remarkable things.
To help you unlock all those powers, though, its a good idea to get a solid understanding of how the Galaxy Tab works, and a look at all its different parts. Youll want to know where all of its buttons, ports, and cameras are located, for examplenot to mention how to get to your Home screen panes, or to a location that will become one of your best friends: the Apps Menu.
On the upper-left rear of your Galaxy Tab as you hold it horizontally, with the small photo lens at the top, you find a small, silver button. It may be only a single button, but its a hard-working one, and it performs several functions:
Sleep/Wake. When your Galaxy Tab is turned on, pressing and releasing the button puts your Tab into Sleep mode, a state in which the display is turned off and the device uses only a minimum amount of power, in order to save battery life. When the Tab is in dreamland, it doesnt register any taps, so you cant accidentally send an email or delete every picture on your Tab. Pressing and releasing this button wakes up the Tab into its locked modeyoull see how to unlock it a little later.
SQL enables you to collect rows into groups and to summarize those groups in various ways, ultimately, returning just one row per group. You do this using the GROUP BY and HAVING clauses, as well as various aggregate functions.
An aggregate function takes a group of values, one from each row in a group of rows, and returns one value as output. One of the most common aggregate functions is COUNT, which counts non-null values in a column. For example, to count the number of waterfalls associated with a county, specify:
Add DISTINCT to the preceding query to count the number of counties containing waterfalls:
The ALL behavior is the default, counting all values: COUNT(expression) is equivalent to COUNT(ALLexpression).
COUNT is a special case of aggregate functions because you can pass the asterisk (*) to count rows rather than column values:
Nullity is irrelevant when COUNT(*) is used because the concept of null applies only to columns, not to entire rows as a whole. All other aggregate functions ignore nulls.