ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/PROG/PASCAL/PASTUT24.ZIP/PTUTRTXT.ZIP/CHAP14.TXT

Text File | 1989-12-01 | 14.9 KB | 355 lines

                                                   Chapter 14
                                     COMPLETE SAMPLE PROGRAMS


Prior to this point, this tutorial has given you many example
programs illustrating a point of some kind, but these have all
been "nonsense" programs as far as being useful.  It would be
a disservice to you to simply quit with only tiny programs to
study, so the following programs are offered to you as
examples of good Pascal programming practice.  They are useful
programs, but they are still short enough to easily grasp
their meaning.  We will discuss them one at a time.



AMORTIZATION TABLE GENERATOR
____________________________________________________________

This is not one program, but five.  Each one is an improvement
on the previous one, and the series is intended to give you
an idea of program development.

AMORT1.PAS - This is the bare outline of the amortization
     program.  Although it is an operating program, it doesn't
     do very much. After some thought and planning, the main
     program was written to allow for an initialization, then
     an annual repeating loop. The annual loop would require
     a header, a monthly calculation, and an annual balance.
     Finally, a procedure was outlined for each of these
     functions with a minimum of calculations in each
     procedure. This program can be compiled and run to see
     that it does do something for each month and for each
     year. It has a major problem because it does not stop
     when the loan is payed off but keeps going to the end of
     that year. The primary structure is complete.

AMORT2.PAS - This is an improvement over AMORT1. The monthly
     calculations are correct but the final payment is still
     incorrectly done. Notice that for ease of testing, the
     loan variables are simply defined as constants in the
     initialize procedure. To make the procedures easier to
     find, comments with asterisks were added. This program
     is nearly usable.  Compile and run it.

AMORT3.PAS - Now we calculate the final payment correctly and
     we have a correct annual header with column headings. We
     have introduced a new variable to be used for an annual
     interest accumulation. This is neat to have at income tax
     time. This program can also be compiled and run.

AMORT4.PAS - This program does nearly everything we would like
     it to do. All of the information needed to build the
     table for any loan is now read in from the keyboard,

                                                    Page 14-1

                                     Complete Sample Programs

     greatly adding to the flexibility. After the information
     is available, the monthly payment is calculated in the
     newly added procedure Calculate_Payment.  The annual
     header has a new line added to include the original loan
     amount and the interest rate in the information. Compile
     and run this program to see its operation.

AMORT5.PAS - The only additional feature in this program is
     the addition of a printout of the results. Examining the
     program, you will notice that many of the output
     statements are duplicated with the Lst included for the
     device selection. Compile and run this program, but be
     sure to turn your printer on to get a printout of the
     amortization table you ask for. If you are using TURBO
     Pascal version 3.0, you will need to either comment out
     line 3 or remove it altogether.



TOP DOWN PROGRAMMING
____________________________________________________________

The preceding example is an example of a top-down approach to
programming.  This is where the overall task is outlined, and
the details are added in whatever fashion makes sense to the
designer.  The opposite is a bottom-up programming effort, in
which the heart of the problem is defined and the rest of the
program is built up around it.  In this case, the monthly
payment schedule would probably be a starting point and the
remainder of the program slowly built up around it.  Use
whichever method works best for you.

The final program AMORT5.PAS is by no means a program which
can never be improved upon.  Many improvements can be thought
of.  These will be exercises for you if you so desire.

1.   In the data input section, ask if a printout is desired,
     and only print if it was requested. This would involve
     defining a new variable and if statements controlling all
     write statements with Lst as a device selector.

2.   Format the printout with a formfeed every three years to
     cause a neater printout. The program presently prints
     data right across the paper folds  with no regard to the
     top of page.

3.   Modify the program to include semimonthly payments.
     Payments twice a month are becoming popular, but this
     program cannot handle them.

4.   Instead of listing the months as numbers, put in a case
     statement to cause the months to be printed out as three
     letter names. You could also include the day of the month
     when the payment is due.

                                                    Page 14-2

                                     Complete Sample Programs


5.   Any other modification you can think up. The more you
     modify this and other programs, the more experience and
     confidence you will gain.



LIST.PAS, to list your Pascal programs
____________________________________________________________

Since the differences between TURBO Pascal versions are
significant, two files are included here.  If you are using
TURBO Pascal 3.0, rename LIST3.PAS to LIST.PAS, and if you are
using TURBO Pascal 4.0 or 5.x, rename LIST4.PAS to LIST.PAS
before continuing on to the next section.

LIST.PAS is a very useful program that you can use to list
your Pascal programs on the printer.  It can only be compiled
with TURBO Pascal because it uses TURBO extensions.  The two
extensions it uses are the string type variable and (in the
case of TURBO Pascal version 3.0), the absolute type variable.
The absolute type variable in line 14 and the coding in the
Initialize procedure is an example of how you can read in the
parameters given on the command line.

If you are using TURBO Pascal 4.0 or 5.x, a completely
different method is used in the Initialize procedure which
should be no problem for you to understand at this point.  To
use this program to print out the last program, for example,
you would enter the following at the DOS prompt LIST
AMORT5.PAS.  This program reads in the AMORT5.PAS from the
command line and uses it to define the input file.  It should
be pointed out that this program cannot be run from a
"compiled in memory" compilation with the TURBO Pascal
compiler.  It must be compiled to a Disk file, and you must
quit TURBO Pascal in order to run it from the DOS command
level.

The parameter read from the command line, AMORT5.PAS, is
stored at computer memory location 80(hexadecimal) referred
to the present code segment.  If you didn't understand that,
don't worry, you can still find the input parameter in any
program using the method given in the initialize procedure for
your version of TURBO Pascal.

If you do not have TURBO Pascal, but you are using MS-DOS or
PC-DOS, you can still use this program because it is on your
disk already compiled as LIST.EXE, and can be run like any
other .COM or .EXE program.  Note that LIST4.PAS is the
version that is compiled and copied on the distribution disk.





                                                    Page 14-3

                                     Complete Sample Programs

TIMEDATE.PAS, to get today's time and date
____________________________________________________________

This is a very useful program as an example of using some of
the extensions of TURBO Pascal if you are using TURBO Pascal
3.0.  It interrogates the inner workings of DOS and gets the
present time and date for you, provided you entered them
correctly when you turned your computer on.  The procedure
Time_And_Date can be included in any TURBO Pascal version 3.0
program you write to give you the time and date for your
listings.  As an exercise in programming, add the time and
date to the program LIST to improve on its usefulness.

The program named TIMEDAT4.PAS does the same thing as the
last, but it works with TURBO Pascal 4.0 or 5.x using the
means of defining a DOS call as it has been revised for the
newer versions.  It turns out to be an almost trivial program
but is still a good illustration of how to use some of the
newer Borland extensions to Pascal.  The observant student
will notice that the time and date procedures have already
been added to LIST4.PAS.


SETTIME.PAS, a useful utility program
____________________________________________________________

This program is very interesting in that it changes the date
and time stamp on any file in the current directory.  It is
the program used to set the time and date on all of the files
on the distribution disks included with this tutorial.  It
sets the time to 12:00:00 and the date to Dec 1, 1989 but you
can use it to set any desired time.


SHAPES3.PAS, an example of menus
____________________________________________________________

This program is not very useful, but it illustrates one way
to handle menus in a Pascal program, but only if you are using
version 3.0 of TURBO Pascal.  Chapter 13 included the
identical program done slightly differently for use with the
TURBO Pascal 4.0 or 5.x compilers.  You can study the
structure and imagine many ways a menu can be used to improve
the usefulness of your own programs.


OT.PAS, The OAKTREE directory program
____________________________________________________________

This program should be very useful to you, especially if you
have a hard disk.  It will list the entire contents of your
hard disk (or floppy) in a very easy to read and easy to use
form.  The program is documented in the file named OT.DOC.
It uses many of the TURBO Pascal extensions and will probably

                                                    Page 14-4

                                     Complete Sample Programs

not compile with any other Pascal compiler without extensive
modifications.

You will find two versions of the source code for this
program, one named OT3.PAS for use with TURBO Pascal version
3.0, and another named OT4.PAS for use with versions 4.0 or
5.x of the TURBO Pascal compiler.  You should rename one of
them OT.PAS for use with your particular compiler.

The two versions are different in a number of ways.  The first
version was written for TURBO Pascal version 3.0 and was only
slightly modified for this new version of the tutorial.  The
newer version, OT4.PAS, was modified extensively to use some
of the procedures provided by Borland such as GetDate,
GetTime, FindFirst, and FindNext.  The program for version 4.0
or 5.x is somewhat smaller since the predefined procedures use
fewer characters to perform a given job, and the executable
version shows an even greater reduction in size.  Apparently
Borland has done a very good job in code size reduction with
the introduction of each new version of TURBO Pascal.

It would benefit you greatly to study the two versions of
OT.PAS side by side and compare the benefits of using the
predefined procedures.

Examine the procedure named Count_Print_Lines in each of the
OT.PAS programs, and you will see a marked difference between
them.  OT3.PAS counts the lines of output, and when it detects
that 55 lines have been output, it makes 11 Writeln calls to
space the paper up to 66 lines.  This works fine for a printer
using continuous form paper, but it doesn't work with a laser
printer that happens to be set to some number other than 66
lines.  For that reason, OT4.PAS uses a form feed after it
detects that 55 lines have been output.  You can choose the
proper OT.PAS program for your compiler and use whichever
paper advance method suits you best.  This is a very useful
program, so you should spend the time necessary to both
understand it and modify it for your own needs.

You will find either program to be a good example of linked
lists because they include a sort routine using a dynamically
allocated B-TREE and another sorting routine that uses a
dynamically allocated linked list with a bubble sort.  These
methods are completely defined in Niklaus Wirth's book,
"Algorithms + Data Structures = Programs", a highly
recommended book if you are interested in advanced programming
techniques.

It might also be pointed out that both OT3.PAS and OT4.PAS
also makes use of recursive methods for both sorting and
handling subdirectories.  It is definitely an example of
advanced programming methods, and it would be a good vehicle
for your personal study.


                                                    Page 14-5

                                     Complete Sample Programs


MOST IMPORTANT - Your own programs
____________________________________________________________

Having completed this tutorial on Pascal, you are well on your
way to becoming a proficient Pascal programmer.  The best way
you can improve your skills now is to actually write Pascal
programs.  Another way to aid in your building of skill and
confidence is to study other Pascal programs.  Many
programming examples can be found in computing magazines and
books.  There are many books available devoted entirely to
TURBO Pascal and you would do well to visit your local
bookstore and review a few of them.

You already own one of the best books available for reference
if you are using TURBO Pascal.  Although the TURBO Pascal
reference manual is worth very little as a learning tool, it
is excellent as a language reference manual.  Now that you
have completed all 14 chapters of this tutorial, you have a
good grasp of the terminology of Pascal and should have little
trouble reading and understanding your reference manual.  Your
only limitation at this point is your own perseverance and
imagination.


OBJECT ORIENTED PROGRAMMING
____________________________________________________________

If you are relatively new to programming, it would be good for
you to completely ignore the last two chapters of this
tutorial until you gain some experience with standard Pascal.
Object oriented programming is a relatively new development,
and although it is a meaningful study, it is totally
unnecessary for small programming projects.  Once your
programs grow to the point where you feel comfortable with a
1000 line Pascal program, you are ready for a study of this
new packaging technique.  Until then, it may only serve to
confuse you.

Whatever your programming level or needs may be, Pascal can
fulfill them and do so in a very elegant way,

Happy Programming.












                                                    Page 14-6