Category : Databases and related files
Archive   : PCDBMS.ZIP
Filename : MANUAL.1

USER'S GUIDE FOR THE
PC-DBMS (TM) DATA BASE MANAGEMENT SYSTEM

version 2.0



(C) COPYRIGHT KWARE, 1985, 1986















Paul Kobrin
Kware
P.O. Box 16206
Arlington, Va. 22215




PC-DBMS DISTRIBUTION NOTICE


PC-DBMS is distributed as user supported software. If you
like it, I ask that you send a voluntary payment of $20.
Please see appendix C for more information.

In any event, you are encouraged to make unmodified copies of
the complete set of distribution files for others.
Commercial sale of PC-DBMS in any manner is prohibited
without Kware's written permission but user groups and
similar non-commercial organizations may impose their
customary charges for copying, etc.



DISCLAIMER


In no event will the author or supplier of this program be
liable to you for any damages, including any lost profits,
lost savings or other incidental or consequential damages
arising from the use of or inability to use this program,
even if the author or supplier has been advised of the
possibility of such damages, or for any claim by any other
party.






PC-DBMS is a trademark of Kware, Inc.
IBM is a trademark of
International Business Machines Corporation.
MS is a trademark of Microsoft Corporation.






CONTENTS













CONTENTS





CHAPTER 1 INTRODUCTION


CHAPTER 2 GETTING STARTED

2.1 SYSTEM REQUIREMENTS . . . . . . . . . . . . . . . 2-1
2.2 DISTRIBUTION DISKETTE . . . . . . . . . . . . . . 2-1
2.3 INSTALLATION . . . . . . . . . . . . . . . . . . . 2-2
2.4 THE INITIALIZATION FILE . . . . . . . . . . . . . 2-3


CHAPTER 3 HANDS ON TUTORIAL

3.1 STARTING THE PROGRAM . . . . . . . . . . . . . . 3-1
3.2 HELP . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.3 COMMAND ENTRY AND EDITING . . . . . . . . . . . . 3-2
3.4 THE OPEN COMMAND . . . . . . . . . . . . . . . . . 3-3
3.5 THE SELECT COMMAND . . . . . . . . . . . . . . . . 3-3
3.6 THE SHOW COMMAND . . . . . . . . . . . . . . . . . 3-6
3.7 THE REMOVE COMMAND . . . . . . . . . . . . . . . . 3-8
3.8 THE DISPLAY COMMAND . . . . . . . . . . . . . . . 3-8
3.9 THE DEFINE COMMAND . . . . . . . . . . . . . . . 3-10
3.10 THE KEY AND DEKEY COMMANDS . . . . . . . . . . . 3-12

3.11 THE EXIT COMMAND . . . . . . . . . . . . . . . . 3-12


CHAPTER 4 GENERAL

4.1 DESCRIPTION OF A PC-DBMS DATA BASE . . . . . . . . 4-1
4.2 LIMITATIONS . . . . . . . . . . . . . . . . . . . 4-1
4.3 DATA FILE STRUCTURE, IMPORT AND EXPORT . . . . . . 4-1
4.4 OBJECT NAMES . . . . . . . . . . . . . . . . . . . 4-2
4.5 THE PC-DBMS EDITOR . . . . . . . . . . . . . . . . 4-2
4.6 COMMAND FORMATTING AND EXECUTION . . . . . . . . . 4-3
4.7 HELP . . . . . . . . . . . . . . . . . . . . . . . 4-4





CHAPTER 5 COMMAND REFERENCE

5.1 OVERVIEW . . . . . . . . . . . . . . . . . . . . . 5-1
5.2 NOTATIONAL CONVENTIONS . . . . . . . . . . . . . . 5-1
5.3 DEFINE . . . . . . . . . . . . . . . . . . . . . . 5-2
5.4 DEKEY . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5 DISPLAY . . . . . . . . . . . . . . . . . . . . . 5-3
5.6 EXIT . . . . . . . . . . . . . . . . . . . . . . . 5-6
5.7 KEY . . . . . . . . . . . . . . . . . . . . . . . 5-6
5.8 OPEN . . . . . . . . . . . . . . . . . . . . . . . 5-7
5.9 OUTPUT . . . . . . . . . . . . . . . . . . . . . . 5-7
5.10 PACK COMMAND . . . . . . . . . . . . . . . . . . . 5-8
5.11 REMOVE . . . . . . . . . . . . . . . . . . . . . . 5-8
5.12 SELECT . . . . . . . . . . . . . . . . . . . . . . 5-9
5.13 SHOW . . . . . . . . . . . . . . . . . . . . . . 5-14
5.14 TOLERANCE . . . . . . . . . . . . . . . . . . . 5-17


APPENDIX A KEYWORDS


APPENDIX B THE RELATIONAL MODEL


APPENDIX C USER SUPPORTED SOFTWARE





























ii













CHAPTER 1

INTRODUCTION



PC-DBMS is a data base management system built on the
relational model. Its features include

- Dynamically formatted full screen forms for data entry,
retrieval and editing and for "fill in the blanks" query
composition.

- A query command that can retrieve selected records from
one or two tables, optionally sorting them.

- Dynamic files, i.e., the capability to create new,
defined tables from query results.

- A fast screen editor for command composition with
previous command recall. The editor features word
wrapping and flying reform.

- A menu-based help system.

- Files containing the data tables look just like the
tables, facilitating import and export.

- Indexing with automatic index update on data entry,
deletion or modification. No operation requires
existence of an index.

- Optional use of color.

- Integrated data dictionary but kept in its own file.

- Entire dbms contained in one EXE file.








1-1














CHAPTER 2

GETTING STARTED



Please read through this section of the manual. Then go on
to run the hands on tutorial in the next section.



SYSTEM REQUIREMENTS

PC-DBMS will run on IBM and true clone computers under
PC/MS-DOS version 2.0 or higher. Minimum memory is 192k.
One disk drive is necessary. A second drive or hard disk is
desirable. Output can be redirected to an optional printer.
Color is vigorously supported but not required.

PC-DBMS operates the video board directly. It will support
IBM monochrome and color graphics boards and close copies of
them.



DISTRIBUTION DISKETTE

The distribution diskette contains the files shown in Table
2-1.
















2-1


GETTING STARTED
DISTRIBUTION DISKETTE



READ.ME printing instructions for this manual
MANUAL.1 first half of this manual
MANUAL.2 second half of this manual
RELNOTES.TXT description of changes in this version

MUSIC.DEF a sample
COMPOSER.DAT data base used
OPUS.DAT in the tutorial

PC-DBMS.EXE the dbms program
MKINI.EXE program to create initialization file
REQUEST.DOC payment form and invoice

Table 2-1. Files on distribution diskette.



INSTALLATION

The installation task copies the files on the distribution
diskette needed to run the tutorial onto another diskette or
onto your hard disk. Then, store the distribution diskette
as a back up. After running the tutorial from the copy,
delete the tutorial's files to save space and continue using
the copy; it will still contain everything needed to use
PC-DBMS.

If you do not have a hard disk, make a diskette copy of the
distribution diskette as follows. Turn on your pc and load
the operating system, i.e, boot it. You will need a
formatted blank diskette. (The IBM Disk Operating System
Manual describes booting and formatting.) Insert the
distribution diskette in drive A:. If you have two drives,
insert the blank diskette in drive B:. In any case, issue
the following copy commands.

COPY A:*.DEF B:
COPY A:*.DAT B:
COPY A:*.EXE B:

If you have a one drive system, A: and B: refer to the
source and distribution diskettes. DOS will tell you how to
swap them in the drive to produce the copy after you issue
each copy command.

After making the copy, put the distribution diskette away and
insert the copy in drive A:. You are ready to run the
tutorial.




2-2


GETTING STARTED
INSTALLATION


If you have a hard disk, it is suggested but not required
that you create a subdirectory for PC-DBMS. It is a
convenient place to keep your data base files and the
program. After booting your system, at the DOS prompt enter
MD\DBMS and when the prompt returns, enter CD\DBMS. You now
have a subdirectory called \DBMS and it is the current
directory.

Whether you created a subdirectory or not, copy the necessary
files to your hard disk. These copy commands assume that the
distribution diskette is in drive A:. If the diskette is in
a different drive, substitute its designation in the
commands.

COPY A:*.DEF
COPY A:*.DAT
COPY A:*.EXE

After making the diskette or hard disk copy, put the
distribution diskette away. On a system without a hard disk,
put the copy diskette in drive A:. You are ready to run the
tutorial.

After you run the tutorial, you might want to delete its
sample data base from the hard disk or diskette copy. On a
system without a hard disk, issue these delete commands.

DEL A:*.DAT
DEL A:*.DEF
DEL A:*.IDX

On a hard disk system, omit the A: in the preceding
commands. The dbms program, PC-DBMS.EXE, will remain on the
copy for your use.



THE INITIALIZATION FILE

When PC-DBMS is run, it presents its welcome screen and then
attempts to find and read a file called PC-DBMS.INI. It
looks first in the current directory and then in directories
specified in the path command. PC-DBMS.INI specifies the
video attributes for elements of the main screen and the
display utility screen. These elements are called screen
items. Video attributes are characteristics such as bright,
color or reverse video. Also, the initialization file can
set the command window editing default to overstrike instead
of pushright.




2-3


GETTING STARTED
THE INITIALIZATION FILE


Without an initialization file, PC-DBMS will use default
video attributes. These defaults do not produce color.
Therefore, creation of an initialization file is highly
recommended on color systems. It is not supplied in the
distribution.

The program MKINI creates an initialization file if none
exists in the current directory. Otherwise, it edits the
file. MKINI can be run from the DOS level by typing MKINI at
the prompt. Alternatively, run PC-DBMS and press the F8 key.

If you have a color graphics adaptor, MKINI will ask if you
also have a color monitor. It then lists the screen elements
one to a line along with their current or default numeric
values and an appearance sample. A palette of choices for
the elements is at the bottom of the screen. Use the
function keys to choose an element to modify. Then type in
the desired number from the palette. Press F10 to exit and
save the file. Press escape to abort.


































2-4














CHAPTER 3

HANDS ON TUTORIAL



This tutorial will acquaint you with the main capabilities of
PC-DBMS in just a few pages. It is cumulative so if this is
your first exposure to the tutorial, go through it in order.
Within in an hour, you'll know the 80% of the program used
95% of the time. If you're already familiar with PC-DBMS,
you might use the tutorial as a refresher. It is organized
by command for convenience.

The tutorial does not cover every command nor does it cover
every feature and limitation of the commands it does cover.
IF A CAPABILITY IS NOT MENTIONED, DO NOT ASSUME IT IS ABSENT.
CHECK CHAPTER 5, COMMAND REFERENCE.

To run the tutorial, you must have the program file
PC-DBMS.EXE and the sample data base files (MUSIC.DEF,
COMPOSER.DAT and OPUS.DAT) all on the disk in the logged
drive.

The tutorial permanently modifies the sample data base so be
sure you are working with a copy of the distribution
diskette.



STARTING THE PROGRAM

Boot your pc as usual. That is, start it and load the
operating system. If you don't have a hard disk, insert the
previously prepared PC-DBMS diskette (see INSTALLATION) into
the default drive, typically A:. If you have a hard disk,
make the subdirectory containing PC-DBMS the default, i.e.,
give the command CD\DBMS at the DOS prompt.

At the DOS prompt (e.g., A>), type PC-DBMS and press return.
The welcome screen appears showing the product name, version
number, etc. Press any key.



3-1


HANDS ON TUTORIAL
STARTING THE PROGRAM


Now the main screen of PC-DBMS appears. At the top left is a
wide window for you to enter commands. Right of it are
function key descriptions. Two stripes the width of the
screen are below the window. You'll see their function soon.
The bottom half of the screen, the output window, displays
data or help messages. The screen is illustrated in Figure
3-1.

---------------------------------------------
: : F1=help
: : F2=rmv help
: COMMAND WINDOW : F3=prev cmd
: : F7=execute
: : F8=config
: : F9=shell
--------------------------------------------- F10=exit
MESSAGE WINDOW STRIPE
COLUMN HEADINGS STRIPE
---------------------------------------------------------



OUTPUT WINDOW





---------------------------------------------------------

Figure 3-1. The main screen of PC-DBMS



HELP

Press the F1 key (top left of keyboard). The help menu's
first page appears in the output window. Get help on
"command entry/editing", the first menu item, by pressing the
first function key, F1. Read the help text in the output
window. The cursor returns to the command window. Try help
on another topic if you like.



COMMAND ENTRY AND EDITING

Whatever you type is entered in the command window. Word
wrapping automatically breaks lines so type the Gettysburg
address without pressing carriage return.



3-2


HANDS ON TUTORIAL
COMMAND ENTRY AND EDITING


Four score and seven years ago, our fathers brought
forth upon this continent a new nation conceived in
liberty and dedicated to the proposition that all
men are created equal ....

Use the cursor keys (numeric keypad arrow keys) to position
the cursor at the "s" in "seven". Now type "twenty-". Next,
delete it by pressing the backspace key repeatedly.

Press the return key. It doesn't initiate command execution;
it never does. It breaks the line at "seven".

Now execute the Gettysburg address like a command by pressing
F7. This is folly so an error message is written onto the
first stripe. That's what the stripe is for.

What happens if you press F3? Try it. (Pressing F7 now will
serve to clear the window.)



THE OPEN COMMAND

PC-DBMS sessions usually begin with the open command. It
makes an existing data base available or starts the process
of creating a new data base. Let's open the sample data base
MUSIC. Type OPEN MUSIC (upper or lower case) in the command
window and press F7 to execute the command. The message
window should read "Database MUSIC opened."



THE SELECT COMMAND

The select command retrieves data from the data base,
displaying it on screen or writing it to a file. The
simplest select command is only two words. Type SELECT
COMP.* and press F7. Figure 3-2 shows the result as
displayed in the output window.














3-3


HANDS ON TUTORIAL
THE SELECT COMMAND



NAME BORN DIED COUNTRY

Tchaikovsky, P. 1840 1893 Russia
Brahms, J. 1833 1897 Germany
Verdi, G. 1813 1901 Italy
Handel, G. 1685 1759 England
Mozart, W. 1756 1791 Austria
Bach, J. 1685 1750 Germany
Chopin, F. 1810 1849 France
Beethoven, L. 1770 1827 Germany
Haydn, F. 1732 1809 Austria
Mendelssohn, F. 1809 1847 Germany
Debussy, C. 1862 1918 France

Figure 3-2. Result of SELECT COMP.*

The data base contains the table COMP whose entire contents
are now in the output window. The table is stored in its own
file. The table has eleven lines called records and four
data columns called fields. Note that ALL can be used in
place of the wildcard *.

Suppose we want only composers born no earlier than 1700.
Press the F3 key to recall the first select command. Press
the numeric keypad's END key to place the cursor at the
command's end. Press the space bar once and type WHERE BORN
>= 1700 so that SELECT COMP.* WHERE BORN >= 1700 is in the
command window. Press F7 to execute it.

The where clause can have up to ten conditions. Recall the
previous command, position the cursor and add AND COUNTRY =
"Germany" so that the entire command is: SELECT COMP.* WHERE
BORN >=1700 AND COUNTRY = "Germany". This command has two
conditions. Press F7. Note that text strings are enclosed
in quote marks. We could connect the conditions with OR in
place of AND. That would change the query's meaning.

Let's retrieve the same data alphabetized. Recall the
previous command, position the cursor at its end, add SORTED
BY NAME and press F7. Note that a where clause, if present,
precedes the sort clause.

It's possible to choose which fields are displayed and their
order. Recall the previous command and edit it to read
SELECT COMP.BORN NAME COUNTRY by using the cursor keys,
backspace and the delete key (Del). Execute the command.

PC-DBMS can calculate new numeric fields from existing ones.
The data base does not give the composers' lifespans but we
can calculate them. Recall the previous command and edit it
to read SELECT COMP.NAME BORN DIED LIFE = DIED- BORN.

3-4


HANDS ON TUTORIAL
THE SELECT COMMAND


Execute the command.

The MUSIC data base also contains the table OPUS. PC-DBMS
permits its contents to be displayed along with the contents
of COMP. Execute SELECT COMP.BORN NAME OPUS.*. Some output
will scroll off screen and what's left is shown in Figure
3-3.

BORN NAME COMPOSER WORK

1685 Handel, G. Beethoven, L. Symphony No. 5
1756 Mozart, W. Brahms, J. Lullaby
1756 Mozart, W. Beethoven, L. Symphony No. 5
1685 Bach, J. Brahms, J. Lullaby
1685 Bach, J. Beethoven, L. Symphony No. 5
1810 Chopin, F. Brahms, J. Lullaby
1810 Chopin, F. Beethoven, L. Symphony No. 5
1770 Beethoven, L. Brahms, J. Lullaby
1770 Beethoven, L. Beethoven, L. Symphony No. 5
1732 Haydn, F. Brahms, J. Lullaby
1732 Haydn, F. Beethoven, L. Symphony No. 5
1809 Mendelssohn, F. Brahms, J. Lullaby
1809 Mendelssohn, F. Beethoven, L. Symphony No. 5
1862 Debussy, C. Brahms, J. Lullaby
1862 Debussy, C. Beethoven, L. Symphony No. 5

Figure 3-3. Result of SELECT COMP.BORN NAME OPUS.*

The composers' birth years and names from COMP were paired
with their names and works from OPUS. Unfortunately,
Debussy's vital statistics were paired with a Beethoven
symphony and so forth. Add the following clause to the
command to match composers only with their own works: WHERE
COMPOSER = COMP.NAME. Execute the corrected command.

Linking related records from different tables is called a
join. Records from the two tables are joined together only
when they have the same composer name, that is, WHERE
OPUS.COMPOSER = COMP.NAME.

Let's look again at the join command: SELECT COMP.BORN NAME
OPUS.* WHERE COMPOSER = COMP.NAME. The first occurrence of
"COMP." (in COMP.BORN) makes COMP the default table.
Subsequent field names not preceded by a table name (NAME)
are presumed to be from COMP. When OPUS.* is encountered,
the default table changes to OPUS. Hence, COMPOSER is
assumed to mean OPUS.COMPOSER.

A field name explicitly qualified by a table name such as
COMP.BORN is called a qualified field name. You can qualify
any field name; the default capability is a convenience to
save typing.

3-5


HANDS ON TUTORIAL
THE SELECT COMMAND


Sometimes a select command retrieves so many records that
they start to scroll off screen. You can freeze the action
by pressing control-NumLock (hold the control key down and
press NumLock once). Then press any key to resume scrolling.
However, to terminate retrieval prematurely, press F10.

You should know about one last select capability. The result
of the select command can become a table in the data base
rather than a display on the screen. Just append a clause
like INTO NU_TABLE to the end of the select command. Then
you can run queries against NU_TABLE or whatever name you
give the new table. Try the previous select command with the
clause INTO JOIN_TBL. Execute another select command against
the JOIN_TBL to confirm its existence. (THIS EXERCISE WILL
PERMANENTLY ALTER THE SAMPLE DATA BASE SO BE SURE YOU ARE
WORKING WITH A COPY.)

One reason to save the query result in a table is to do a
three way join such as to join together tables A, B and C.
The select command accepts no more than two table names
before the into clause. So use a select command to join A
and B INTO X. Then use a second select command to join X and
C.



THE SHOW COMMAND

So far we have discovered two tables in the MUSIC data base.
Are there others? Type SHOW and press F7. The result is in
Figure 3-4. In fact, there are 3 tables.

TABLE NAME FILE RECORDS FIELDS EOR MODIFIED

COMP COMPOSER.DAT 11 6 2 11-25-1984
OPUS OPUS.DAT 2 2 2 11-25-1984
JOIN_TBL JOIN_TBL.DAT 2 4 2 12-15-1984

Figure 3-4. Result of SHOW

The recall and default table capabilities and the command
editor save typing. Keyword truncation saves typing, too.
Any keyword longer than 3 characters can be truncated to 3 or
more characters. For example, SHO has the same meaning as
SHOW. Try it!

Keywords are the boilerplate of commands. Examples are
select, show, open and into. The names of data bases
(MUSIC), tables (COMP) and fields (BORN) are not keywords.
Neither are field values such as "Germany". Don't truncate
names and values, only keywords.


3-6


HANDS ON TUTORIAL
THE SHOW COMMAND


The show command can retrieve additional information about
the tables in the data base. Try SHO\DESCRIBE. It brings up
verbal descriptions of the tables.

Show can also retrieve information about fields. Execute
SHO\FIELDS but press control-NumLock before any output
scrolls off screen. When ready, press any key to resume
scrolling. The entire result is shown in Figure 3-5.

FIELD NAME TYPE KEY FROM TO



TABLE COMP

NAME T N 1 19
BORN N N 20 23
filler1 F N 24 24
DIED N N 25 28
filler2 F N 29 29
COUNTRY T N 30 44


TABLE OPUS

COMPOSER T N 1 19
WORK T N 20 44


TABLE JOIN_TBL

BORN N N 1 4
NAME T N 5 23
COMPOSER T N 24 42
WORK T N 43 67

Figure 3-5. Result of the command SHO\FIELDS

Consider COMP. It has two fields, filler1 and filler2, which
have been hidden so far. That's because they are filler or F
type fields. The fields which select has displayed are
either text (T) or numeric (N). All the fields in MUSIC are
not KEYed (N), i.e., there are no indices yet. The last two
columns give the beginning and ending character positions in
the file for each field.

Finally, verbal descriptions of fields can be retrieved.
Execute SHO\FIE\DES.

Any of the four show command forms can be followed by one or
more table names. Then, only the information for the
indicated table(s) will be retrieved. For example, try

3-7


HANDS ON TUTORIAL
THE SHOW COMMAND


SHO\FIE COMP.

The show command displays the contents of the data
dictionary, known as the schema. PC-DBMS uses the schema
internally.



THE REMOVE COMMAND

The table JOIN_TBL you created with a select command keeps
appearing when show commands are executed. Let's remove it
from the schema. Execute REMOVE JOIN_TBL and try a show
command to confirm the deletion. The file JOIN_TBL.DAT which
contained the table is not deleted. Only the schema is
altered.



THE DISPLAY COMMAND

The display command invokes the display utility to add,
delete or modify records. The utility automatically creates
a full screen data entry form.

[THE FOLLOWING EXERCISES WILL PERMANENTLY MODIFY THE SAMPLE
DATA BASE. BE SURE YOU ARE USING A COPY.]

Suppose we want to add a record to the COMP table. Execute
DISPLAY/INPUT COMP and watch the data entry screen appear.
Note that INPUT appears at the bottom right. Field names are
placed next to blocks for field values.

The display utility has its own help; press F1. After you
read the help text on screen, press any key to restore the
data entry form.

Let's enter a record for another composer. In the block
marked NAME, type Dvorak, A. Then press tab. The cursor now
jumps to the BORN block. Enter 1841 and press tab. Enter
the entire four field record:

Dvorak, A. 1841 1904 Czechoslovakia

If you entered a field incorrectly, return to it by pressing
F9 or tab repeatedly. Then type over the erroneous entry.
The cursor keys will move you around within each field block.
Try editing even if you didn't make an error.

Press F7 to add this record to the COMP table. The record
will be stored if the two numeric fields contain numbers. If
there is a defective entry for a number, an error message

3-8


HANDS ON TUTORIAL
THE DISPLAY COMMAND


will appear on the bottom line and the cursor will be placed
in the offending field block for you to make a correction.

After adding a record, the field blocks are cleared so you
can enter another record. For now, press F10 to leave the
display utility and return to the main screen. If you like,
confirm the addition of Dvorak's record by executing SELECT
COMP.*.

Now, let's use the display utility to fix the error in
Beethoven's record. Execute DIS\EDIT COMP and note that the
same data entry screen reappears except now it shows QUERY at
the bottom right rather than INPUT.

First, we have to find Beethoven's record. Then we have to
edit and store it. The QUERY screen finds records which are
then displayed on the EDIT screen.

Beethoven was born in 1770 so we will find all records
containing a birth year of 1770. This will bring up
Beethoven's record and possibly others. Tab to the BORN
field block on the QUERY screen and enter 1770. Press F7 to
start the search for 1770 records.

At the bottom right, QUERY changes to EDIT and a 1770 record
appears. It's Beethoven's record. Tab to the COUNTRY block.
Beethoven lived mainly in Austria, not Germany. Make the
change by typing over the incorrect entry. Press F6 to save
the corrected record. If you wanted to delete the record,
you could press F4 instead. Or you could press F7 to leave
it intact. Here are the choices:

F4 = delete record \
F6 = change record to edited one > & display next record
F7 = leave unchanged /
F10 = leave unchanged, return to QUERY screen

F4, F6 and F7 cause display of the next 1770 record, if there
is one. However, Beethoven's is the only 1770 record so the
screen clears and a message "No more records" appears. Press
any key. The QUERY screen reappears. You can now repeat the
cycle of finding records (QUERY screen) and correcting them
(EDIT screen).

From the QUERY screen, you can exit to the main screen by
pressing F10. Do so.







3-9


HANDS ON TUTORIAL
THE DEFINE COMMAND


THE DEFINE COMMAND

The define command invokes the define utility which adds
definitions of tables and their fields to the schema. The
utility consists of two prompting screens. The first screen
is used to describe a table. The second screen is for
describing a field.

Let's define a new table with two fields. Execute DEFINE.
The first of the prompting screens replaces the main screen.
It asks a sequence of four questions about the new table.
Figure 3-6 shows the screen with all questions answered.
Complete your screen similarly. Use the backspace and cursor
keys for editing. The second screen appears when you press
return after the last question.

---------------------------------------------------------

DESCRIPTION OF NEW TABLE


Name of table: ORCHESTRAS

File spec of file to hold ORCHESTRAS:
ORCHSTRA.TXT

Enter description of table (optional):
INFORMATION ABOUT SOME ORCHESTRAS

Enter code for record terminator: 2 0 Nothing
1 Carriage return
2 Carriage return-
line feed



F10 to quit
---------------------------------------------------------

Figure 3-6. The define utility's first or table
definition screen

Note that the file-spec ORCHSTRA.TXT abbreviates "orchestra"
to comply with the eight character file name limit.

The second screen asks a sequence of five questions about the
new tables's first field. Figure 3-7 shows the screen with
all questions answered. Complete your screen similarly.





3-10


HANDS ON TUTORIAL
THE DEFINE COMMAND


---------------------------------------------------------

DESCRIPTION OF FIELD


Name of field: ORCHESTRA
Data Type Choices
Enter first letter of data type: T Text Number Filler


How wide in characters is field ORCHESTRA? 25

Index field (Y/N)? N

Enter description of field (optional):
THE ORCHESTRA'S NAME, E.G., CHICAGO SYMPHONY





F10 to stop defining fields
---------------------------------------------------------

Figure 3-7. The define utility's second or field
definition screen

When you press return after the last question, the same field
definition screen restarts so you can define the second
field. Complete it. Here are the five questions and answers
for the second field.

FIELD NAME CONDUCTOR
DATA TYPE T
FIELD WIDTH 19
INDEX N
VERBAL DESCRIPTION Last name, first name of
music director

The field definition screen is now prompting for another
field's description but we're finished. To terminate the
field definition cycle, press F10.

Now the first or table definition screen reappears. You
could define another table and its fields but we're done.
Press F10 to exit the definition utility and restore the main
screen.

Try SHO\FIELDS ORCHESTRAS to confirm addition of the new
table to the schema. If you want, add records to the table
with DIS\INPUT ORCHESTRAS.


3-11


HANDS ON TUTORIAL
THE KEY AND DEKEY COMMANDS


THE KEY AND DEKEY COMMANDS

PC-DBMS can index a field. The index or key works like a
book's index; it speeds searches. In addition, a key can
provide a sorted retrieval without doing a sort.

You can tell if a field is keyed from the KEY column in the
SHOW\FIELD command's output. See Figure 3-5.

If a field is keyed, its index will be updated whenever a
value in that field is added, deleted or changed by the
display utility. Index updating slows file maintenance and
indices use disk space so only certain fields should be
keyed.

A field starts life without indexing if created by the SELECT
... INTO command. It may start out indexed if created by
the define utility. See Figure 3-7's fourth question.

If a field does not already have an index, you can give it
one with the key command. Execute KEY COMP.NAME. Confirm
the indexing with SHOW/FIE COMP. Try SELECT COMP.* SORTED BY
NAME. The retrieval will be sorted and a little faster than
without the key. The speed up is dramatic on tables with
many records.

You can remove a key with the dekey command. Execute DEKEY
COMP.NAME. Now try SELECT COMP.* SORTED BY NAME. Did you
notice the slow down?

Indexing is especially important in joins. Consider SELECT
COMP.* OPUS.WORK WHERE OPUS.COMPOSER = COMP.NAME AND BORN >
1800. The join condition, OPUS.COMPOSER = COMP.NAME, will
process much more quickly if at least one of the two fields
is keyed. The COMP.BORN condition also will process more
quickly if that field is keyed.

However, the where clause exploits no more than one index per
table. Hence, keys will be most used if they're on fields in
different tables, e.g., on OPUS.COMPOSER and COMP.BORN.

Indexing is never necessary in PC-DBMS. It only accelerates
processing, sometimes dramatically, though.



THE EXIT COMMAND

There is an exit command but the simple way to execute it is
to press F10. You're now back at the DOS level.



3-12















CHAPTER 4

GENERAL



DESCRIPTION OF A PC-DBMS DATA BASE

A PC-DBMS data base consists of three kinds of files. The
data base definitions (schema) reside in one file that has a
"DEF" extension. Its file name is the name of the data base.
This file must exist.

The data of a data base are in named tables that have records
and fields. Each table resides in its own file. Nothing
else is in these files. The name of the file may be
different from the name of the table it contains. There may
be any number of data files associated with a data base.

Indices are in the third type of file. There may be zero or
one index files for each data file. Each index file holds
the indices for all the keyed fields of the corresponding
data file. The drive designation, directory (both optional)
and file name of the index file are the same as the drive,
directory and file name of the corresponding data file.
However, the index file's extension is IDX.



LIMITATIONS

Each table may have up to 32767 records including deleted
records. Each record may have up to 999 fields. The schema
file holds up to 32767 records. It uses one record for each
table and another for each field. Deleting definition
records (with the remove command) does not reduce the count.



DATA FILE STRUCTURE, IMPORT AND EXPORT

Each data file contains the entirety of one table and nothing
else. The file is an ASCII representation of the table.
That is, there is no packing or data compression and numbers

4-1


GENERAL
DATA FILE STRUCTURE, IMPORT AND EXPORT


are represented as text, not in binary or other format.

The use of ASCII files to represent tables facilitates import
and export of tables between PC-DBMS and other applications.
The show\fields command is used to obtain the definition of a
table for export. Use the define utility to describe an
imported table to PC-DBMS.

Indices may be unreliable if an indexed table is altered by
another program. Indices should be rebuilt. Also, record
counts exhibited by the show command are not reliable on
tables supplied or altered externally. However, the
erroneous record count is innocuous.

PC-DBMS flags a deleted record by placing a backslash (\) in
the first character position.



OBJECT NAMES

The names of data bases, tables and fields consist of
alphanumeric characters and the underscore (_). The first
character of a name must be alphabetic. Do not use PC-DBMS's
keywords as names. See Appendix A. Although PC-DBMS will
accept non-conforming names, the consequences are
unpredictable. Case does not matter. Data base names are
1-8 characters. Table and field names are 1-16 characters.
However, tables created by the select ... into command are
limited to 1-8 character names.

Most commands use "qualified field names." A qualified field
name is a field name preceded by the name of its table and a
period. For example, COMP.BORN is the field BORN from the
table COMP.



THE PC-DBMS EDITOR

Upon invoking the program, its main screen will appear. A
framed window is at the top left. Commands are typed into
it. A word processing type editor operates in the command
window. The same editor operates in the field blocks of the
data entry form created by the display command. The
following describes the editor.

There are two modes, insert and replace. The default mode is
insert in the command window. The cursor is "low" in this
mode. Pressing the "Ins" key toggles between the modes. In
the display utility, only the replace mode is available and
the cursor is "high."

4-2


GENERAL
THE PC-DBMS EDITOR


In insert mode, each entered character pushes those after it
rightward. If a word would be pushed out of the display
area, a flying reform occurs. That is, the last word is put
at the beginning of the next line (word wrap) and all text
that was on that line is pushed right which may cause word
wrap and reform of the following line and so forth.

In replace mode, an entered character replaces the one that
was at the cursor.

The following applies to both modes.

The delete key deletes the character under the cursor and the
backspace key deletes the preceding character. The line is
closed up in either case by shifting subsequent characters
left.

The four cursor keys function. The Home and End keys move
the cursor to the beginning and end of the current line. The
Page Up key moves the cursor to the first position in the
window or field block.

Carriage return breaks a line at the cursor. That is, all
characters at and after the cursor are shifted to the next
line. A flying reform will occur. (Carriage return does not
initiate command execution.)



COMMAND FORMATTING AND EXECUTION

Commands may spread over as many lines as necessary. There
is no continuation character.

Words or items in a command are separated by one or more
spaces. The space is the only separator recognized by
PC-DBMS.

Numbers may be preceded by a sign and may contain a decimal
point. They may be followed immediately by "E" or "e" and a
signed or unsigned integer to obtain scientific
representation. For example, VELOCITY > 3.35E+11.

Character strings must be entered in quotes. For example,
NAME = "Smith". Use a pair of quotes to embed a quote mark
in a string. For example, NAME = "Herman ""Babe"" Ruth".

Comments, which are ignored by PC-DBMS, may be placed in
commands. They are preceded by an apostrophe ('). A comment
ends a command.



4-3


GENERAL
COMMAND FORMATTING AND EXECUTION


PC-DBMS keywords may be entered in upper, lower or mixed
case. They may be truncated to three or more characters.

The F3 key clears the window and puts the previous command
into it for possible editing.

The F7 key executes the command in the window. (Carriage
return is used for editing only.) If the command is flawed,
an error or warning message will be issued. Command
execution is aborted if there is an error. If only a warning
is given, execution will proceed. Most messages are errors.

The F8 key invokes the MKINI configuration program to create
or edit the initialization file PC-DBMS.INI. (See
INSTALLATION.)

The F9 key creates a new DOS shell. The screen will clear
and the DOS prompt will appear. To return to PC-DBMS, type
"exit" at the prompt.

The F10 key executes the exit command, terminating the
program and returning the user to the operating system.



HELP

A help facility is available in the main screen. Press F1 to
obtain the first page of a multi-page menu of help topics.
The menu and cursor appear in the bottom half of the main
screen, occluding any data display that was there.

Cycle through the menu pages by pressing F9 or quit help by
pressing F10. Obtain the help message on a menu item by
pressing the function key (F1-F8) corresponding to that
item's menu number (1-8). The message remains in the bottom
half of the main screen although the cursor returns to the
command window.

The data display occluded by the help menu and messages can
be restored by pressing F2.












4-4