CD Actual 15/CDACTUAL15.iso/cdactual/program/pascal/PAS_TUT.ZIP/CHAP16.TXT

Text File | 1991-02-04 | 11.3 KB | 295 lines

                                                       Chapter 16
                                         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, greatly

                                                        Page 16-1

                            Chapter 16 - Complete Sample Programs

          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 16-2

                            Chapter 16 - 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
_________________________________________________________________

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 a TURBO extension, the string type variable.

The method used in the Initialize procedure to read the command
line parameter 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 are not using a TURBO Pascal compiler, but you are using
MS-DOS or PC-DOS, you can still use this program because it is
provided on your disk already compiled as LIST.EXE, and can be run
like any other .COM or .EXE program.



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.  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 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.  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 LIST.PAS.


                                                        Page 16-3

                            Chapter 16 - Complete Sample Programs


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 disk included with this tutorial.  It sets the time
to 12:00:00 and the date to Feb 4, 1991 but you can use it to set
any desired time.



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 not compile with any
other Pascal compiler without extensive modifications.

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 this program to be a good example of linked lists
because it includes 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 OT.PAS 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.



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.



                                                        Page 16-4

                            Chapter 16 - Complete Sample Programs

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 16
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.

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

Happy Programming.










































                                                        Page 16-5