PD Collection CD 1/PD Collection CD 1.iso/data/powerbas/Docs/!Tutorials

Text File | 1995-08-21 | 45KB | 901 lines

Tutorials for Powerbase

Powerbase is an extremely powerful program. Despite the fact that it is
actually very easy to use its complexity and many features can make it
difficult for the new user to get started. This booklet uses some ready made
example databases supplied on the distribution disc to help familiarise you
with the main functions of the program.

It is made up of two sections. The first is a Quick Tutorial aimed at
inexperienced users who may not have used a database before. The Main
Tutorial is meant for people who, although new to Powerbase, have some
familiarity with other databases. If you do fall into this category you
should skip the Quick Tutorial and move straight on to the Main Tutorial.



Quick Tutorial

This tutorial is intended to acquaint the new user as painlessly as possible
with the most commonly-used facilities of Powerbase. It does not explain how
to create a database from scratch (see Chapter 4 − Creating a New Database −
in the Manual), nor does it delve into the many advanced features, but it
does explain how to:−

(a)     Start up Powerbase and open an existing database.

(b)     Browse through the database and search for individual records.

(c)     Add new records and alter or delete existing ones.

(d)     Query the database to create simple reports.

(e)     Close the database.

The supplied sample database Friends is used to illustrate most of these
activities. If you have a hard disc you should copy Friends and Powerbase
itself onto it before proceeding further. It is possible to use Powerbase
from floppy discs only but some operations, such as printing lists, will be
quite slow. Unless memory is very tight users of floppy discs are
recommended to allocate at least 32K to the RAM disc and copy Friends onto
it. Everything will then run much faster. Powerbase can provide
context-sensitive help via Acorn’s !Help application and you are advised to
load this, resizing the help window and placing it at the top right of the
screen. Further help can be had by choosing the Help entry which will be
found on Powerbase’s main menu and also on the icon-bar menu.

1  Starting Powerbase

Double-click on the Powerbase icon. After a few seconds it will appear on
the icon-bar with the words “No data” beneath it to show that no database is
open. Dragging the Friends icon onto the Powerbase icon on the icon-bar will
open Friends for use and the words “No data” will be replaced by the name of
the database.

Two windows will open. One is the record window and displays the first
record in the database, the one for Badgery Peter. The other is the keypad
which allows you to control the browsing, searching and editing functions of
Powerbase. The keypad is rather large and obscures quite a big area of the
record window. The most-used buttons, however, are on the top two rows and
the keypad can be moved part way off screen to get it out of the way.

2  Browsing and Searching

Now that you have a database running we will find out how to move from
record to record and how to access any specific record by using a small
group of letters called the key of the record.  All the mouse clicks
referred to are made with the SELECT (left) button. If the chosen keypad
action has an obvious opposite then you will find that using the ADJUST
(right) mouse button brings about that effect.  e.g. While SELECT on the top
left keypad button takes you to the start of the file, ADJUST on the same
keypad button takes you to the end.

2.1 Browsing through the Records

The top row of buttons on the keypad allows you to browse through the file.
If you have !Help running, as previously suggested, it will tell you what
each button does. Once you get the general idea you will find the symbols on
the buttons logical and self-explanatory. The most commonly used ones act as
follows:−

(a)     The arrows at the ends of the row take you to the first and last
records. You are at the first record now, so click with SELECT on the
top-right button and you will see the record for Turnip Charles. The
leftmost button takes you back to the start again.

(b)     Movement through the file one record at a time is achieved using the
single arrow keys next door to the ones you have just used. Try them out,
noting the way records come up in alphabetical, or reverse alphabetical,
order.

(c)     The keys with double arrows let you make longer jumps through a
file. The number of records skipped is shown in the writable icon between
them and has a default value of 10. As there are only 10 records in Friends
these keys will have the same effect as the “first” and “last” keys, unless
you make the interval smaller. Click in the icon, delete the 10 and enter 5
or 2, then try the double-arrow keys again.

2.2 Searching for a record

The fifth button on the second row of the keypad shows a question mark
followed by a “record card” icon. We will call it the Search button. When
clicked with SELECT a small window opens on the right-hand side of the
keypad. This is the Search window and contains a writable icon in which to
enter the key of the record you wish to display.  In this database keys are
made up from the first 4 letters of the surname plus the initial so, if you
wanted to call up the record for Bloggs Fred you would need to enter BLOGF.
Do so then click on Find (or type the Return key on the keyboard) and the
record will be displayed. Note that the key is shown in the window heading.

If you enter the key of a non-existent record Powerbase displays the record
which most nearly matches the key, but flashes the key field to warn you
that what is being displayed is not what you asked for.

3  Editing the Database

This part of the tutorial involves changes to the data. Make a working copy
of the disc and put the original in a safe place. If you are using a copy of
Friends on the RAM disc then the floppy disc won’t be altered, but it’s
still not a good idea to work with the original disc.

3.1 Modifying records

Point the mouse at any field and click SELECT. The red text caret will
appear in the field. The contents of the field may now be edited with the
aid of the keystrokes which are standard for all RISC OS writable icons.
i.e.

Ctrl U  clears the field.

Delete  removes the character to the left of the caret.

Copy    removes the character to the right of the caret.

Shift Copy      deletes the word to the right of the caret.

Ctrl Copy       deletes everything from the caret to the end of the line.

 <=⇦ and => ⇨   move the caret left/right by one character.

Shift <=⇦ and Shift=>⇨  move the caret left/right by one word.

Ctrl <=⇦ and Ctrl =>⇨   move the caret to start and end of the field.

Having modified one or more fields you may be wondering what you have to do
to make Powerbase save the modified record so that the changes won’t be
lost. You don’t need to do anything! Powerbase will ensure that your changes
are saved when you display a different record or close the database.

3.2 Recovering data after a mistake

You may edit the wrong field by mistake and want to restore the previous
contents. Call up Bloggs Fred’s record and change the address from “12
Woodland Road  Exeter” to “12 Woodville Road  Exmouth”.  Now click MENU over
the first line of the address. The second entry on the main menu (Field)
contains a short group of letters called the tag of the field, in this case
ADD1. Follow the right-pointing arrow to the Field sub-menu and choose the
last entry; Undo changes. The contents of the field will revert to “12
Woodland Road”. Notice that only the first line of the address is affected;
the town is still “Exmouth”.  If you want to restore that field as well
click MENU over it and follow the procedure just described.

There might be occasions when you make a hopeless mess of a record and want
to discard all the changes and revert to what you started with.  You could,
of course, “undo” each field separately as we just did for the street
address and town but there’s a quicker way.  Look near the bottom of the
main menu, (just above Help) and you will see that here too is an Undo
changes option. Choosing this undoes all the alterations you have made.

It is important to realise that these facilities depend on the fact that
Powerbase holds the currently-displayed record in memory and will therefore
only work if the altered record has remained on display from the time you
started changing it up to the point where you decided to “undo”. If you have
looked at another record or clicked on Force update in the meantime then the
changes will have been written to the disc and thus become “permanent”.

3.3 Adding and deleting records

To add a new record we use the Add record button which looks like a plus
sign and an index card. Clicking on this offers a blank record into which
you can type new data. You don’t have to complete all the fields, in fact
the only field into which you must type something is the NAME field. This is
the key field; the one from which the key, mentioned earlier, is derived. If
you leave the key field blank then nothing will be written to the database.

Type the name “Bodmin George”, then go to the beginning of the file and step
through it record by record. You will find that your new record has been
inserted in the correct place, i.e. the sequence goes: Badgery, Bloggs,
Bodmin, Cavendish.

Now try deleting the record you’ve just added. There is a “dustbin” button
which will do exactly that, but don’t use it just yet. Make sure that the
unwanted record is on the screen and click the button to the right of the
dustbin. You will now find that Bodmin’s record has vanished; the names now
run straight from Bloggs to Cavendish, just as they did before you added
Bodmin.

This looks a bit too easy. Suppose you clicked the keypad button by mistake
and deleted an important record?  No problem; what you have just done has
been made easy because it’s far less drastic than it looks. The record
hasn’t really been deleted at all. Click the button above the one you used
for “deleting”. This shows a green right-pointing arrow and a card index
icon. “Bodmin” will reappear. You will soon find, however, that it appears
to be the only record in the file! Don’t worry; nothing has been lost. A
Powerbase database is treated as six separate subfiles numbered 0−5. When
you first open the database you are looking at Subfile 0 and the heading of
the record window shows this. If you look at the heading now you will see
that it has changed to Subfile 1.

The buttons on either side of the bin carry pictures which suggest their
true functions. They do not delete records; they merely move records from
one subfile to another. The right button moves the displayed record to the
next subfile in sequence. Thus, in the above case the “Bodmin” record has
been moved from subfile 0 to subfile 1. A record in subfile 1 would be moved
to subfile 2 and so on. When it gets to 5 the next click moves it into
subfile 0 where it was originally. As you may have guessed, the left button
moves records in the opposite direction, i.e. from subfile 1 to 0 or from
subfile 0 to 5.

If you do want to lose a record for good you consign it to the dustbin.  As
this button’s action is more drastic than that of the other two you are
given a chance to change your mind. A window  headed Powerbase: please
confirm: will appear displaying the question Delete record permanently?
Clicking OK causes the record to be deleted, Cancel removes the warning
window from the screen leaving the record untouched.

4  Printing Lists

Before Powerbase can produce a list it must be told:−

•       which fields should appear on the list

•       which records should appear on the list

4.1 Making the field selection

Specifying the fields you want is extremely easy. To include a field point
at it and click with ADJUST. The selected field will then appear with its
foreground and background colours reversed. If you change your mind you can
de-select it by clicking on it again with ADJUST. The order in which you
select the fields is the order in which they will appear in the printed
list. Take care with this as there is nothing on the screen to indicate what
order the fields will be in. Field selections may be saved (using Save
selection from the Print submenu) and reloaded for future use. For now
select the name and the first 3 fields of the address.

4.2 Choosing which records to print

Specifying which records to print is somewhat more complicated, although
efforts have been made to render it as simple as possible. With the mouse
pointer in the record window click MENU. This displays the main Powerbase
menu from which you should choose Print. A small window appears in which you
can specify the criteria which must be met by records for inclusion in the
list. If you just click over the Print button (or type Return) without
entering anything, you will obtain a list of the whole database (or, more
accurately, of the the whole of the current subfile). Try this first.

When the search is complete the list will be displayed in a window. If you
point to a record in the list and double-click with SELECT Powerbase will
display the chosen record in the main record window. Note that the caret is
placed in the field you were pointing to on the list. This is very useful if
you spot errors in the data whilst examining a list. A double click on the
offending item offers the record with the caret correctly positioned for
editing.

Most queries involve printing only some of the records, not the whole
database. To target a particular group of records we need to enter a search
formula which will distinguish the records we want to print from all the
rest of the records. Search formulae can be quite complex and a more
detailed treatment is given in the Manual. Only a few simple examples are
shown here.  Enter the following and then click Print:−

ADD2=Exeter

The report window appears showing just one record: the one for “Bloggs
Fred”. ADD2 is called the tag of the field. The label which appears beside a
field on the screen is called its descriptor and you might have expected
such labels to be used to refer to fields in search formulae. This is not
done for two reasons:−

(1)     Descriptors can be inconveniently long for use in this way.

(2)     Fields don’t necessarily have descriptors. Of the 5 address fields
only the first has a descriptor (Address). Since every data field needs a
“handle” of some sort so that we can include it in search formulae we give
each a tag, which is never more than 4 characters. Clicking MENU over a
field makes its tag appear in the second menu item.

The record for “Bloggs Fred” is, however, not the only one with an address
in Exeter. There is another (“Sunningdale Samantha”) but with Exeter in
ADDR3 rather than ADDR2. You can print both on the same list by using the
formula:−

ADD2,ADD3=Exeter

Notice the way the alternative tags are separated by commas. We call this a
tag list. A record will be printed if any one of the tags in the tag list is
matched. The part of the search formula after the = sign is called the
target and here too we may specify several in a target list. Try the
following:−

ADD3=Exeter,Anytown

and also:−

ADD2,ADD3=Exeter,Anytown

The first of these examples prints the records for “Soap Joe” and
“Sunningdale Samantha”, the second prints these two and “Bloggs Fred” as
well. What the second formula is saying is “Print all the records which have
either ‘Exeter’ or ‘Anytown’ in either the ADD2 or ADD3 field”.

The characters we want to match don’t, of course, always make up the entire
field. You can also search for part of a field. Suppose you wanted the
records for people called Peter, Fred and Jean. Enter the formula:−

NAME{Peter,Fred,Jean

and you will find that the records for “Badgery Peter”, “Bloggs Fred” and
“Ford Jean” are printed. The curly bracket (“{”) means “contains”. i.e. the
name field doesn’t have to consist of Peter, or Fred or Jean, but has to
contain one of these names somewhere within it.

4.3 Hard copy

So far you have displayed reports in a window. If you want to send them to
your printer run !Printers, switch on the printer, then click MENU over the
displayed report. The Save as text option leads to a standard Save box from
which you can drag the file icon to !Printers on the icon-bar. You could
also drag it to a directory window to save it. Or you could simply type
Return, in which case the report would be saved under a suitable default
name in a directory called PrintJobs inside the Friends database directory.
Every Powerbase database has a PrintJobs directory to use as a general
dumping ground for reports and which needs to be cleared out periodically.

5  Closing down

A database may be closed down by choosing the Close database entry from the
icon-bar menu. When you do so all relevant data stored in memory is saved to
disc and the database is closed. You do not have to do anything to save the
database file itself to disc since it has been there all along. Only the
current record is in memory at any one time and this is automatically
written back to disc when it has been changed in any way.

There’s also an Abandon database entry on the icon-bar menu. This too will
close your database but without saving new data to the disc. It is really
intended as the quickest way to close a database which you have opened
simply for examination. If you are entering data for real you should use
Close database.

If you are going to use another database straight away just double click on
it or drag it to the Powerbase icon on the icon bar. In fact you don’t even
need to close the previous database before doing this; Powerbase will do it
for you.

When working with a database on the RAM disc Powerbase will issue a warning
that the data is not secure and that you need to drag it from the RAM disc
to a floppy or hard disc before switching off.

To terminate Powerbase itself use the Quit option on the icon bar menu.



Main Tutorial

This section is intended to acquaint a new user with the most commonly-used
facilities of Powerbase. It does not explain how to create a database from
scratch but it does explain how to:−

(a)     Start up Powerbase and open an existing database.

(b)     Browse through the database and search for individual records.

(d)     Add new records and alter or delete existing ones.

(d)     Query the database to create simple reports.

(e)     Close the database.

The sample database Elements is used to illustrate these activities. If you
have a hard disc copy Elements and Powerbase itself onto it before
proceeding further. It is possible to use Powerbase with floppy discs but
some operations, such as printing lists, will be slow. Unless memory is very
tight users of floppy discs are recommended to allocate at least 112K to the
RAM disc and copy Elements onto it, which will make it much faster.
Powerbase can provide context-sensitive help via Acorn’s !Help application
and you are advised to load this, resizing the help window and placing it at
the top right of the screen. Further help can be had by choosing the Help
entry on Powerbase’s main menu or on the icon-bar menu.

1  Starting Powerbase

Double-click on the Powerbase icon. After a few seconds it will appear on
the icon-bar with the words “No data” beneath it to show that no database is
open. Dragging the ‘Elements’ icon onto the Powerbase icon on the icon-bar
will open Elements for use and the words “No data” will be replaced by the
name of the database. Double-clicking on the Elements icon has the same
effect, in fact if Powerbase isn’t already on the icon-bar a double-click on
Elements will install it for you provided that the Powerbase icon has been
seen by the filer.

Two windows will open. One is the record window and displays the first
record in the database. The other is the keypad which allows you to control
the browsing, searching and editing functions of Powerbase. The keypad is
rather large and obscures quite a big area of the record window. The
most-used buttons, however, are on the top two rows and the keypad can be
moved part way off screen to get it out of the way.

2  Browsing and searching

Now that you have a database running we will find out how to move from
record to record and how to access any particular record by using a small
group of letters called the key of the record.  All the mouse clicks
referred to are made with the SELECT (left) button. If the chosen keypad
action has an obvious opposite then you will find that using the ADJUST
(right) mouse button brings about that effect.  e.g. While SELECT on the top
left keypad button takes you to the start of the file, ADJUST on the same
keypad button takes you to the end.

2.1 Browsing through the records

The top row of buttons on the keypad allows you to browse through the file.
If you have !Help running, as previously suggested, it will tell you what
each button does. Once you get the general idea you will find the symbols on
the buttons logical and self-explanatory. The most commonly used ones act as
follows:−

(1)     The buttons at the far left and right take you to the beginning and
end of the file. The rightmost button takes you to ZIRCONIUM and the
leftmost one to ACTINIUM.

(2)     Single arrows move by one record at a time. From ACTINIUM, clicking
the right arrow takes you to ALUMINIUM. The left arrow takes you back to
ACTINIUM.

(3)     Double arrows move through the file by longer jumps The right double
arrow takes you from ACTINIUM to BISMUTH and the left one back to ACTINIUM.
The “fast forward/rewind” value is shown in the box between these “fast
wind” buttons. It is initially set to 10 but can be altered by clicking in
it with SELECT and entering a new value.

At either end of the file “wrap around” occurs. If you are at the last
record (ZIRCONIUM) one record forward takes you to ACTINIUM again.
Similarly, one record back from ACTINIUM goes to ZIRCONIUM.

The second row has buttons marked like the “play” and “stop” controls of a
cassette player. Play allows an automatic flip-through of the records
without the need to touch any other buttons. When you get to the place you
want, click on Stop. If the records go past too quickly you can slow the
process down by increasing the number in the central icon of the top row of
buttons. (This is normally used to set the “fast-wind” interval; see above.)

2.2 Key fields, Keys and Indices

When using the six buttons on the top row of the keypad you will have
noticed that the records appear to be arranged alphabetically by the name of
the element. The actual order in which records occur in the file is in fact
nothing like alphabetical, but the order in which they are accessed is
determined by an index which forces them to appear in alphabetical order.
Every database must have at least one index, but you can have as many extra
ones as you wish (subject to memory and disc limitations).

The second row of the keypad has two buttons featuring a blue arrow with a
key symbol. Click on the right one and the record for HYDROGEN is displayed!
If you now experiment with the top row of buttons as before you will find
that the records no longer appear in alphabetical order of name but in order
of ATOMIC NUMBER instead. What we have done is change to a different index.
If a database has several indices the “key” buttons allow you to cycle
through them in opposite directions. (Since Elements has only two indices
the two buttons have exactly the same effect.) When you change to a
different index the screen always displays the first record as determined by
that index.

An index is built from keys which are derived from a particular key field.
The two indices used by Elements are based on the NAME and ATOMIC NUMBER
fields. The way in which the key stored in the index is derived from the key
field differs in the two cases. For the NAME index the first four letters of
the name are used. Since no two elements have names beginning with the same
four letters this gives a unique value for the key. (Two letters would not
be enough because of names like CHLORINE and CHROMIUM.) The ATOMIC NUMBER
index is based on the whole 3-digit maximum length and the ordering is
numeric. Whenever a record is displayed the key is shown in the window title
(# characters are for padding and should be ignored.)

The record screen shows which fields are key fields and which are not. The
labels, or descriptors, of fields are normally black. Where the fields are
key fields they are shown in dark blue instead and the field used by the
current index has its descriptor in red. Note also that the background
colour of the NAME field is pale yellow whereas the rest are white . This
indicates that NAME is the primary key field. The primary key is more
important than the others. The index based on it is the only one which a
database must have and is the one selected when a database is first opened.

2.3 Searching for a record

The fifth button on the second row of the keypad shows a question mark
followed by a “record card” icon  We will call it the Search button. When
clicked with SELECT a small window, the Search window, opens to the right of
the keypad. It contains a writable icon in which to enter the key of the
record you wish to display. Suppose you want to see the record for the
element NITROGEN. If the current index is the NAME then enter NITR and
either type the Return key on the keyboard or click the Find button with
SELECT. The required record quickly appears. If you enter the key of a
non-existent record Powerbase displays the record which most nearly matches
the key, but flashes the key field to warn you that what is being displayed
is not what you asked for. You don’t necessarily need to type the whole key;
NIT would do in this case, but NI would be ambiguous (there are elements
called NICKEL and NIOBIUM).

To find NITROGEN when the ATOMIC NUMBER index is active you would need to
know that the atomic number of nitrogen is 7. Change key, enter this number
and type Return or click on Find. The required record appears. Abbreviated
keys are not allowed in this case for obvious reasons; if you want element
103 (LAWRENCIUM) it’s no good entering 10 (NEON)!

You might want to examine a group of related records, e.g. the six similar
elements LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM and FRANCIUM which
are known as the Alkali Metals. You could, of course, look up each in turn
by entering its key but there is a better way. Click on the Use filter
button on the keypad. The button becomes ticked and the Filter window opens
on the right of the keypad. This button is what we call an option switch and
is used to turn a particular feature ON or OFF. The six elements referred to
all occur in group 1 of the Periodic Table of the elements so type GP=1 into
the writable icon. and click on Filter.  The record for CAESIUM is
displayed.  If you experiment with the buttons on the top row of the keypad
you will find that they behave as if the six Alkali Metals were the only
elements in the database; all the rest have been “filtered out” so that you
access only the ones you are interested in.  To return to normal operation
either click the Cancel button on the Filter window or turn off the switch
on the keypad.

3  Editing the Database

This part of the tutorial involves changes to the data records. Make a
working copy of the disc and put the original in a safe place. If you are
using a copy of Elements on the RAM disc the floppy disc won’t be altered,
but it’s not a good idea to work with the original disc.

3.1 Modifying records

Pointing the mouse at any field and clicking SELECT places the caret in that
field. The contents of the field may then be edited in the standard way for
RISC OS writable icons. i.e.

Ctrl U  clears the field.

Delete  removes the character to the left of the caret.

Copy    removes the character to the right of the caret.

Shift Copy      deletes the word to the right of the caret.

Ctrl Copy       deletes everything from the caret to the end of the line.

 <=⇦ and => ⇨   move the caret left/right by one character.

Shift <=⇦ and Shift=>⇨  move the caret left/right by one word.

Ctrl <=⇦ and Ctrl =>⇨   move the caret to start and end of the field.

Changes made to a record cause the record to be written back to the database
whenever you display a different record or close the database. There is a
button on the keypad called Force update but you don’t normally need to use
it.

3.2 Using the scratchpad

It is sometimes necessary to copy the contents of one field into another,
either in the same record or a different record. This can be done with the
aid of the scratchpad which is controlled by the two buttons at the ends of
the third row on the keypad. Place the caret in the field you want to copy
and click on the left button. This stores the contents of the field on the
scratchpad. Moving the caret to another field and clicking the right button
copies the data from the scratchpad into that field, over-writing its
previous contents. You may continue to “paste” the data into new fields as
often as you like. Only when you click the left button again are the
contents of the scratchpad changed. Data pasted into a field will not be
allowed to overflow; if too long for the field it will be cut to the
permitted length. As an added precaution you can’t paste into a field if
there is nothing on the scratchpad so accidental blanking of fields is
avoided.

3.3 Undoing mistakes

You might edit the wrong field by mistake and want to restore the previous
contents. Click MENU over the field. The second entry on the main menu
contains the tag of the field. Follow the right-pointing arrow to the Field
sub-menu and choose Undo changes. The previous contents of the field will be
restored. Similarly, if you make a mess of a whole record and want to go
back to the way it was you can choose Undo changes from the main menu.

It is important to realise that the Undo facilities will not work if you
have looked at another record before using them (or clicked on Force
update). You can only recover data which has been altered in or removed from
the currently-displayed record.

3.4 Adding new records

First we will add a new record for a fictitious element as described below:−

        NAME            TASMANIUM

        SYMBOL                  Ts

        ATOMIC NUMBER   108

The second button on the second row of the keypad has a plus sign and a
“record card” icon. This is the Insert button. A blank record will be
displayed with the caret in the NAME field.  Enter TASMANIUM here and type
Return. The caret will jump to the SYMBOL field. Enter Ts. You will now need
to press Return twice to get to ATOMIC NUMBER (One press takes you to the
un-named field after NAME where the origin of the element’s name is given.)
Alternatively you could point the mouse at the ATOMIC NUMBER field and click
SELECT. There is no need to press Return after entering a field in order to
accept the data; it’s just the most convenient way of getting to the next
field.  When entering data into widely-scattered fields it is more
convenient to use the mouse to move the caret.

Having entered the data click any of the first row of buttons so a different
record is shown. Now use Search to find TASMANIUM by name (its key will be
TASM). Change to the other index and find it by atomic number. In both cases
try moving to the record just before and just after the new one, noting that
it has been placed in its correct position in both indices: between TANTALUM
and TECHNETIUM in the NAME index and at the end of the ATOMIC NUMBER index.

3.5 Data Input Validation

When entering the above data you may have noticed that the NAME field will
only accept capital letters and the ATOMIC NUMBER field will only accept
numerals. Any others are simply ignored. We call this feature character
validation.

Another level of data validation, which we will now illustrate, is called
table validation  Make an entry in the GROUP field. Type X, for example,
then try to move to another field by either typing Return or clicking the
mouse. You will find that you can’t do so; you get an error message instead.
This is because the GROUP field is linked to a validation table which means
that only entries which appear in the table may be used in that field.
Fields linked to validation tables are distinguished by using dark green,
instead of black, as the foreground colour.

To see what the validation table contains, place the caret in the GROUP
field then click on the List values button on the keypad. The validation
table will be displayed in its own window. Only items in the left column of
the table may be entered in the GROUP field. Element 108 would be a
transition metal, so enter T. You will now find that Powerbase accepts your
data.

Both character validation and table validation may be turned off and on by
means of a switch on the Preferences window. To get at this window click
MENU over the Powerbase icon on the icon-bar and choose  Preferences  from
the icon-bar menu. The rather large window which appears has a collection of
option switches down its left-hand side. The sixth of these (Validate input)
is normally ON to indicate that validation is in effect. Click to turn it
off then click on Accept. The Preferences window will be removed from the
screen and you will find that input is no longer being validated.

3.6 Deleting records

Since “tasmanium” isn’t a real element we want to remove it from our
database. There is a “dustbin” button  which will do exactly that but we
won’t use it just yet.  Make sure that the unwanted record is on the screen
and click the button to the right of the bin. You will now find that
TASMANIUM has vanished; the names run from TANTALUM to TECHNETIUM and the
atomic numbers end with 103, just as they did before you added the extra
record.

What if you had clicked the button by mistake and deleted an important
record? Powerbase handles this very nicely. The record hasn’t really been
deleted at all. To prove this, click on the button above the one you used
for “deleting”. This shows a green right-pointing arrow and a “card index”
icon. TASMANIUM will reappear. You will also find that it appears to be the
only record in the file! Don’t worry; nothing has been lost. A Powerbase
database is treated as six separate subfiles numbered 0-5. When you first
open the database you are looking at Subfile 0 and the heading of the record
window shows this. If you look at the heading now you will see that it has
changed to Subfile 1.  The button you hav just clicked advances the subfile
number by 1.  Its counterpart on the left has the opposite effect.

The buttons on either side of the bin carry pictures which suggest their
true functions. They do not delete records; they merely move records from
one subfile to another. The right button moves the displayed record to the
next subfile in sequence. Thus, in the above case TASMANIUM has been moved
from subfile 0 to subfile 1. A record in subfile 1 would be moved to subfile
2 and so on. When it gets to 5 the next click moves it into subfile 0 where
it was originally. As you may have guessed, the left button moves records in
the opposite direction, i.e. from subfile 1 to 0 or from subfile 0 to 5.

If you do want to lose a record for good you consign it to the dustbin.  As
this button’s action is more drastic than that of the other two you are
asked to confirm that this really is what you want to do before the deletion
goes ahead.

4  Printing Lists

Before Powerbase can produce a list it must be told:−

•       which fields should appear on the list

•       which records should appear on the list.

4.1 Making the field selection

Specifying the fields you want is extremely easy. To include a field point
the mouse at it and click with ADJUST. The selected field will appear with
its foreground and background colours reversed. If you change your mind
about a field you can de-select it by clicking on it again with ADJUST. The
order in which the fields will appear in the printed list is the order in
which you select them. Take care since there is nothing on the screen to
indicate what order the fields will be in.  The fields chosen for inclusion
in a printout make up a selection which may be saved, using Save selection
from the Print submenu, and reloaded for future use. Just for now select
NAME, SYMBOL and GROUP.

4.3 Choosing which records to print

Specifying which records to print is more complicated, although efforts have
been made to render it as simple as possible. With the pointer in the record
window click MENU. This displays the main Powerbase menu from which you
should choose Print. A small window appears in which you specify the
criteria which must be met by records for inclusion in the list. If you just
click the Print button (or type Return) without entering anything here you
will obtain a list of the whole database (or, more accurately, the the whole
of the current subfile). Try this first.

Nothing will be printed until the search is complete. If the mouse pointer
is over the main window the hourglass will tell you how far things have
progressed. Pressing Escape will cause the process to be aborted. When
complete the list will be displayed in a window. Clicking MENU over it
displays a menu which leads to a Save box. You may  save the list as a text
file by dragging the file icon to a filer window or print it by loading
!Printers and dropping the file icon on the !Printers icon on the icon-bar.

If you point to a record in the displayed list and double-click with SELECT
Powerbase will display the chosen record in the main record window. Moreover
the caret is placed in the field you were pointing to on the list. This is
very useful if you spot errors in the data whilst examining a list. A double
click on the offending item offers the record with the caret correctly
positioned for editing.

Most database queries don’t, of course, involve printing all the records.
You will usually need to enter a search formula before clicking Print. You
have already used a search formula when you typed GP=1 to “filter out” all
but the six Alkali Metal records (see 2.3). Search formulae can be complex
and a more detailed treatment is given in the Manual. Only a few simple
examples are shown here.

Suppose we want a list of all transitional elements. i.e. all those which
have T in the GROUP field. We can do this by entering the search formula:−

GP=T

Why GP?  GROUP=T seems the more obvious choice but Elements contains many
fields which have no label, such as the one on the first line which gives
the origin of the element’s name. Every field which can hold data has to
have a handle by which we can refer to it and that handle is called the
field tag. Tags are very short; never more than four characters. You have
seen some tags already. Look at the list you printed earlier. The three
columns are headed with the tags (NAME, SYM and GP) not the descriptors
(NAME, SYMBOL and GROUP). We therefore meets tags in two contexts:−

•       specifying fields in search formulae

•       as the default column headings in lists

The Print options window, displayed by choosing Options from the Print
submenu, lets you change the column headings to field descriptors if you
prefer them.



Type GP=T in the space provided and click Print. This time the list will be
a much shorter one and you will see that the GP column contains T in every
case.

The second example involves printing all elements whose names end in “IUM”.
What we need to specify is that NAME contains IUM and we do this by entering
the search formula:−

NAME{IUM.

Note the use of a left brace (curly bracket) to mean “contains”.  Another
way to perform this search is to use a wild-card. Type:−

NAME=$IUM

Clicking Print will produce the same list as before. The “$” is a wild-card
character which can represent any number of unspecified characters. The
search formula is saying in effect, “I don’t care what the first part of the
name is as long as it ends with IUM”.

We will combine the previous two examples into a two-pronged search for all
the TRANSITIONAL elements whose names end in “IUM”. The search formula this
time is either:−

NAME{IUM AND GP=T

                or:−

NAME=$IUM AND GP=T

Note the spaces before and after AND. These are essential. You might like to
try an alternative way of entering a search formula. Proceed as follows:−

1.      Click the Help button on Print window. This opens the Help window.

2.      NAME should already be visible as the required field, but you need
to select the radio button for contains.

3.      Click in the space next to Value and enter IUM.

4.      Click Add to formula.  The search formula now reads NAME{IUM.

5.      Click the AND button.

6.      Click on the “menu” button to the right of the tag display and
choose item 6 (GP)

7.      Select the radio button for is equal to

8.      Enter T in the Value field.

9.      Click Add to formula

The complete search formula should now be visible so click Print and the
list will be produced. The procedure takes far longer to describe than to do
and can be a great help to the infrequent Powerbase user who has trouble
remembering the syntax of search formulae. If you use complex queries often
you may find it convenient to save them for future use. Save query from the
Print submenu enables you to do this.

The biggest problem you are likely to encounter is not knowing the tags for
the various fields. By using the above method you can see all the tags
displayed in a menu or cycle through them using a pair of arrowheads called
“bump” icons. It is also useful to know that clicking with SELECT on a field
while holding down Ctrl causes the tag of that field to appear in the search
formula icon.

5  Merging data into an Impression document

The distribution disc contains a simple Impression document called
MergeTest. It will be used in conjunction with the Elements database to
illustrate direct data-merging with Impression.

(1)     Ensure that Impression has been “seen” by the filer. (You need not
actually load it.)

(2)     Open the Elements database and drop MergeTest onto the record
window. The Data merge window will appear.

(3)     Click on Merge. You will see that data relating to the record for
ACTINIUM has been inserted into the Impression document.

(4)     The arrow and double-arrow buttons, identical to those on the
keypad, may be used to move through the database merging different records
into the document.

(5)     A search formula may be used to restrict the operation to records
matching certain criteria.

(6)     Print may be used to print the document with the currently-merged
data. To print a set of documents, one for each matching element, select
Print all then click on Merge.



During data-merging Impression editing is disabled; you can’t place the
caret in the document and the mouse pointer appears as a red and blue cross.
Clicking on Cancel or closing the Data merge window restores normal editing.

For more information on data-merging, including instructions on how to
prepare the Impression document, see Ch 9 in the Manual.

6  Closing down

A database may be closed down by choosing the Close database entry from the
icon bar menu. When you do so, all the indices stored in memory are saved to
disc and the database is closed. You do not have to do anything to save the
database itself to disc since it has been there all along. Only the current
record is in memory at any one time and this is automatically written back
to disc when it has been changed in any way.

Also saved automatically is the link file which holds the relational links
between the main database and the validation tables. The tables themselves
are also saved.

There’s also an Abandon database entry on the icon-bar menu. This too will
close your database but without saving new data to the disc. It is really
intended as the quickest way to close a database which you have opened
simply for examination. If you are entering data for real you should use
Close database.

If you are going to use another database straight away just double click on
it or drag it to the Powerbase icon on the icon bar. In fact you don’t even
need to close the previous database before doing this; Powerbase will do it
for you.

When working with a database on the RAM disc Powerbase will issue a warning
that the data is not secure and that you need to drag it from the RAM disc
to a floppy or hard disc before switching off.

To terminate Powerbase itself use the Quit option on the icon bar menu.