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MANUAL.1
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THE VISIBLE-PASCAL MANUAL
(C) Copyright 1984, William Hapgood
all rights reserved
William Hapgood Associates
10 Sycamore Road
Wayland, MA 01778
PREFACE
VISIBLE-PASCAL is user-supported software. While it is
copyrighted by the author, you are authorized and encouraged
to copy and distribute the disk with the Visible-Pascal
program files on it, provided that you do not distribute any
files that have been modified, and that you distribute all
the files on the disk. If you find it useful, you are
encouraged to send a contribution ($35 suggested) to the
author. If you include your name and address, you will
receive a future update. Comments on features you would
like to see in Visible-Pascal or reports on program bugs or
other problems are always welcome, too.
REQUIRED EQUIPMENT
You can run VISIBLE-PASCAL on IBM-PC (or compatible)
computers, including the IBM-PCjr, with 128K of memory, at
least 1 disk drive, and DOS 2.0 or higher. If you write
programs that use graphics, then a graphics display adapter
is required (this is built into the PCjr).
You CAN use, if you want: both mono and graphics adapters; a
printer; or more than 1 disk drive, including a hard disk or
RAM disk.
An 80 column display is suggested, but not required.
TABLE OF CONTENTS
CHAPTER 1: INTRODUCTION
CHAPTER 2: GETTING STARTED
CHAPTER 3: LET'S RUN A PROGRAM
CHAPTER 4: SCREEN PLAY
CHAPTER 5: AN INTRODUCTION TO EDITING
CHAPTER 6: ADVANCED EDITING
CHAPTER 7: RUNNING VISIBLE-PASCAL PROGRAMS
CHAPTER 8: VISIBLE-PASCAL SYNTAX
CHAPTER 9: TECHNICAL DETAILS AND INSTALLATION
CHAPTER 10: SUMMARIES OF DEMONSTRATION PROGRAMS
CHAPTER 11: PRETTY PRINTING
CHAPTER 12: CUSTOMIZING THE KEYBOARD
CHAPTER 1: INTRODUCTION
Pascal is a programming language that is being used more and
more today, both in education (for example, the College
Entrance Examination Board offers an advanced placement test
based on Pascal) and in industry (many programs you see in
computer stores were written in Pascal). Pascal is both
well-structured (which means that the logic of the program
you want to write can be easily written in Pascal) and
powerful (which means that large and complex programs can be
written in it). It is a good idea to learn Pascal: it is a
good example of what programming is about; and if you choose
to become a programmer, it is a language which you can use
in your career.
VISIBLE-PASCAL is a special version of Pascal, with the
purpose of giving the first-time Pascal programmer an easy
time writing and programming his or her first programs.
There is a lot to keep straight when you first start
programming, and a professional version of Pascal can be
very confusing at first. VISIBLE-PASCAL helps in 3 ways.
First, Visible-Pascal makes writing and changing your
programs simple by including an editor which is very easy to
learn how to use.
Second, Visible-Pascal makes running your programs simple by
giving you single keystroke commands to RUN or EDIT your
program.
Third, Visible-Pascal makes fixing your programs simple by
showing you the operation of your program as it runs. This
is the reason why VISIBLE is in the name of this system. It
is as if you were learning how a car works by watching a
transparent model of the engine, and could observe the
valves work and pistons move in front of you and in slow
motion.
Who should use VISIBLE-PASCAL? YOU should, if one of these
cases applies to you:
--First, if you want to learn enough about Pascal to find
out what programming is about, or are curious to see how it
differs from BASIC, then Visible-Pascal will show you this
quickly and easily.
--Second, if you want to learn Pascal to write serious
programs, such as for a career or for the CEEB test,
Visible-Pascal will both make it easy to start and will show
you exactly how Pascal statements work. You may eventually
move on to a 'production' Pascal to write large or involved
programs; however, you will probably always use the
Visible-Pascal editor as your favorite tool.
--Third, if you teach programming, Visible-Pascal will allow
you to demonstrate the internal workings of a Pascal program
for your students, and answer the question: 'What is the
program we wrote doing NOW?'
One final word before you begin. Learning to program a
computer is not easy. You have to learn many details all at
once: how to operate the computer, what disks and disk files
are, how to use the keyboard, the rules of the programming
language, what to do when something happens that you don't
expect, and on and on. Don't get discouraged when you don't
learn it all in one day: NO ONE DOES! Try to use several
different ways to learn about computers and programming:
practice with programs like Visible-Pascal, read a good book
about your computer or about Pascal, asks friends to help
you, or join a computer society. Be patient; soon you will
pick up the new information and start to feel more
comfortable with computing.
CHAPTER 2: GETTING STARTED
The VISIBLE-PASCAL distribution disk contains a number of
files; some are the Visible-Pascal system itself, some are
demonstration programs for you to try while you are learning
how to use the system, and some are required for starting up
your computer with the necessary parts of DOS (the operating
system that runs your computer). It is not legal to
distribute Visible-Pascal disks with any of the DOS programs
on it (they belong to IBM), so unless someone has added the
required DOS files to your Visible-Pascal disk for you, you
will have to do this before starting to use Visible-Pascal.
This is a difficult step for a beginner, so I will describe
the operations that need to be done, and either someone who
knows something about the computer and using DOS will need
to do these steps for you, or you will have to refer to the
DOS manuals that came with your computer for help with some
steps.
1. I recommend that you make a copy of the Visible-Pascal
disk, and keep the original put away 'just in case'. To make
a copy, you will need to run the DOS program called
DISKCOPY. To do this, after you see A> on your screen
a) put your DOS disk (version 2.0 or higher) in drive A;
b) type DISKCOPY A: B:
c) follow the instructions for putting disks in your
disk drives. The Source diskette is the Visible-Pascal
disk; the Target diskette is the new disk. If you need
help, your DOS manuals will help you do this; the procedure
differs a little depending whether you have 1 or 2 disk
drives in your computer.
2. Now you need to put the operating system files onto the
Visible-Pascal disk that you will be using. To do this,
after you see A> on your screen
a) put your DOS disk in drive A;
b) if you have 2 disk drives, put your new
Visible-Pascal disk in drive B;
c) type SYS B:
d) type COPY COMMAND.COM B:
e) type COPY ANSI.SYS B:
If you are told to switch disks in steps c, d, or e (this
will happen if you have only 1 disk drive), follow the
instructions.
3. Re-boot the computer by pressing Ctrl-Alt-Del.
If you have all the required files on the disk, you should
see a welcome message and a list of the demonstration files
that are on the disk. If you have a problem at this point,
read chapter 9 on installation.
CHAPTER 3: LET'S RUN A PROGRAM
In this chapter I will show you how to start VISIBLE-PASCAL
and how to RUN and EDIT a simple program, and what happens
when the program contains an error. You will run a program
called SOUNDS that comes with Visible-Pascal.
Start by placing your Visible-Pascal working disk (the one
you made in chapter 2) in drive A of your computer. If the
computer if off, turn it on; if the computer is already on,
press Ctrl-Alt-Del to reset it. You should see a welcome
message, a list of program files that are on the disk,
instructions on how to print this manual, and a request for
your command:
Command?
A>
When you see this, Visible-Pascal is ready for you.
FIRST TIME THROUGH THE SOUNDS PROGRAM:
stepping through 1 statement at a time.
Type:
RUN SOUNDS
and then press carriage return <CR>. Now you will see
Visible-Pascal get the program SOUNDS ready to run. First
it checks for errors; then, if there are no errors it shows
you a copy of the program with the first line that will
execute highlighted. There is a menu of commands at the
bottom of the screen; we will learn some of them in this
chapter.
Pascal, like any language, has grammar rules that you have
to follow to write correct programs. I won't try to teach
you the Pascal rules in these chapters - there are some good
books that can help you with this. I will help you see how
programs execute and how to use Visible-Pascal to learn what
your programs are doing.
As you look at the program SOUNDS, notice the line that is
highlighted:
DURATION := 500;
This line is the way Pascal tells the computer to make the
variable DURATION take on the value (become equal to) 500.
Notice that on the 4th line of the program the variable
DURATION is declared to be an integer; when a program
starts, all integers are given the value 0, and this value
is shown inside angle brackets to the right of the
declaration:
DURATION : INTEGER; <<0>>
Visible-Pascal shows you the current values of variables by
putting the value on the screen like this automatically.
You can run the program one line at a time and see what
happens at each step. To do this, press <space>, the space
bar, once.
The highlighting moves to the next line, and you see that
the value of DURATION has indeed changed from 0 to 500:
DURATION : INTEGER; <<500>>
Press <space> once more and see what happens to the value of
NOTE.
Now the line that is highlighted is:
TONE(NOTE,DURATION);
This statement uses the TONE command which is part of
Visible-Pascal; TONE needs two pieces of information to
work: a NOTE and a DURATION of the note. This statement
shows the way this is written using Pascal's rules.
Press <space>. Did you hear the note? If your computer's
speaker is working, you should! Continue to press <space>
through the rest of the program until the line
Program complete.
appears. As you use <space> to step through the program,
watch the value of NOTE change, and listen to the tone that
is produced at each TONE statement.
SECOND TIME THROUGH THE SOUNDS PROGRAM;
Watching a program run in slow motion.
Type:
RUN SOUNDS <CR>
again. Again Visible-Pascal gets the program ready to run.
You know how to step through the program one statement at a
time with the space bar, so this time try a new command:
press 'W', which stands for 'Watch the program'.
Visible-Pascal does the stepping for you, and you can watch
the program run in slow motion. Notice how the value of NOTE
in the 3rd line of the program changes.
THIRD TIME THROUGH THE SOUNDS PROGRAM;
Running at full speed.
Type:
RUN SOUNDS <CR>
again. Now you will try the R for Run command, which runs
the program at full speed without giving you the special
Visible-Pascal aids. Press 'R' and listen to the program
execute. You see only a blank screen because Visible-Pascal
doesn't display a program when you Run it, and the SOUNDS
program doesn't write anything on your computer screen
itself. Soon, however, you will see how easy it is to put
statements in a program that write to the screen.
FOURTH TIME THROUGH THE SOUNDS PROGRAM;
learning to edit by making mistakes!
To learn to write your own programs you must learn how to
create and modify programs like SOUNDS. You can start by
modifying SOUNDS like this:
Type:
EDIT SOUNDS <CR>
Now instead of Visible-Pascal getting SOUNDS ready to run,
you will use the editor to make changes in the program. The
chapters on the editor will explain how to use it fully; for
now, we will use just a few commands to change the SOUNDS
program and re-run it.
The editor shows you the SOUNDS program, much as it did when
running it, except that there are only two lines of menu
information at the bottom of the screen. The editor uses the
underline blinking cursor to control where you make editing
changes; right now, it should be under the 'P' of PROGRAM on
the first line of the screen. To add characters at this
location, all you need to do is type, so try typing 'X' and
a space. PROGRAM becomes X PROGRAM; since this violates one
of the rules of Pascal (namely, that all programs begin with
the word 'program'), your program is no longer correct.
Let's see what happens when you try to RUN it.
To run a program after editing it, do the following:
1) Press <Esc> and you see a menu of editing
commands;
2) Press the <F1> function key to use the filing
system;
3) Press 'R' to select Replace and Run.
Visible-Pascal will check the program for errors, as before,
but this time it finds one and puts you back editing, with
an error message and a pointer to the place where the error
was discovered:
X PROGRAM SOUNDS;
^
-----Error at or before this line:--------------
'PROGRAM' expected.
Correct the program and RUN it again!
Visible-Pascal is pointing to the word 'X' and saying that
it expected to find the word 'PROGRAM' at this point. To
correct this error, delete the character 'X' by pressing the
<Del> key once.
Now re-run the program by doing the same three steps you did
before:
<Esc>, <F1>, and 'R'.
Now the program should run correctly as it did at the
beginning of the chapter.
In this chapter you learned how to RUN a program, and how to
EDIT one; you learned how to step through a program with
<space>, how to WATCH a program, and how to RUN one at full
speed. You learned how to insert and delete characters with
the editor, and how to fix an error and re-run the program.
In the next chapter, we will see some more ways to RUN a
program, and see how a program can write on the computer's
screen.
CHAPTER 4: SCREEN PLAY
When you write programs, you will often want to print things
on the computer's screen and have the program use things
that you type at the computer's keyboard. In this chapter,
we will use a small program called WORDS to learn how to do
these operations. You will also learn more about running
programs.
To get started, let's type:
RUN WORDS <CR>
The program that is displayed on your screen uses several
statements that write on the screen; it also reads
information from your keyboard. To start, type <space>.
Since the highlighting moved down a line, the line:
WRITELN('this is the WORDS program;');
should have executed. However, it says to WRITE a LiNe on
the screen, and you don't see any new line of text on the
screen, do you? Well, the reason is this: Visible-Pascal is
using the screen to show you the program and the variables
and the command menu; there is no place to put the line that
the program is supposed to WRITE! And here is the solution:
Visible-Pascal uses one 'screen', and the program that is
running uses another. You can switch between them whenever
you like; Visible-Pascal keeps track of the information that
is on each screen, so that you don't have to. There are two
'information screens' in use, and either one of them can
show on your computer's 'physical screen' as you wish.
To switch from the screen you see now (let's call this the
command screen) to the one with the results of the program
that is running (let's call this the program screen), just
press 'S'. You should see the line:
this is the WORDS program;
press 'S' again to see the command screen. Press 'S' some
more to get used to it; when a program is writing
information to the screen, watching both the command and
program screens by switching between them like this is very
useful.
Switch to the command screen; press <space> again; switch to
the program screen and see the new line added to it.
Step through the program with <space> until the highlighted
line is:
READLN(COUNT);
Switch to the program screen; it looks like the program is
asking you to type in a number, doesn't it? Switch back to
the command screen and press <space> one more time. The
lower menu region is replaced with this:
------------------------------------------------------
Program is requesting input!
------->_
which is your cue to type in the number that the program
wants. You must also press <CR> at the end of typing stuff
for a READLN statement. Until you type <CR>, you can
back-space to correct errors; the <CR> sends your number,
etc. to the program.
Note now that on the command screen, the variable COUNT has
taken on the value that you typed in. Switch to the program
screen; your number is there, too.
Switch to the command screen and step the program along
through a FOR statement, which is used to do something
several times. The program is not 'stuck' on one line; it
is executing that line the number of times that you typed
in. You can switch to the program screen anytime to check
on what is happening.
RUN WORDS again, and this time give the 'W' command to Watch
the program. Everything you did above will happen
automatically. But you will never get to see the program
screen if you let the program run automatically until it is
finished. One way you can get to see the program screen is
to press <Ctrl-Break> when the FOR statement is executing.
This stops the program, and you can switch screens then. You
will learn another way, later.
Finally, RUN WORDS again, and this time give the 'R' command
to run the program at full speed. Now you see only what the
program was written to do, with no aid from Visible-Pascal.
Congratulations! You are doing quite a lot with Pascal,
especially if you have not yet read the chapters on editing
or running programs or on the syntax of Visible-Pascal. At
this point you can either continue reading this manual, or
jump right in, using the built-in menus to guide yourself.
There are other demonstration programs listed in chapter 10
you can try; and you can edit any of the programs if you
wish. However, note that Visible-Pascal does not contain
every language feature of full Pascal, so you will need to
skim the syntax chapter sooner or later. You will also want
to read about the extras in Visible-Pascal that are missing
in standard Pascal, such as color, graphics, and sound!
CHAPTER 5: AN INTRODUCTION TO EDITING.
The Visible-Pascal editor makes the job of writing and
modifying Pascal programs really easy. These instructions
are in two parts: this introduction tells you how to begin,
and ADVANCED EDITING tells about powerful features that make
editing larger programs a breeze. You should read it after
you feel comfortable using the basics.
PRELIMINARIES.
These instructions assume that your keyboard is an IBM-PC
one; for the PCjr, you have to learn some special key
combinations to use for the function keys, etc. For all
computers, we will use the following abbreviations for some
of the keys:
CR means press the carriage return key;
BS means press the backspace key;
ESC means press the escape key;
DEL means press the delete key;
F1 means press function key F1 (or F2..F10);
CTRL-x means hold the Ctrl key and press x (like
SHIFT);
ALT-x means hold the Alt key and press x.
STARTING and LEAVING the editor.
To edit a file that is named (or will be named) 'MYFILE',
just type
EDIT MYFILE
'MYFILE' can be an old file (already on your disk) or new
(not yet there). If it is an old file, the editor will
present you with its first page (screenful), and you can
begin editing. If it is new, the editor will beep at you and
give you a blank screen to write on.
To leave the editor when you are done, press function key F1
to bring the filing system menu to the screen.
(Forgot which key?? Press ESC for some memory jogs!)
Now press 'R' to Replace your disk file with an updated
copy, leave the editor, and Run your program.
ENTERING text.
The first step in writing a program, using any editor, is to
type in your program. Use CR to start a new line, and BS to
backspace over typing mistakes as you go. The blinking
cursor shows where the next letter you type will go; the
'shadow' cursor shows where the end of the current line is.
--Note that CR starts a new line under the start of the one
above; this AUTO-INDENTING makes neat program writing easy.
You can adjust the margin with spaces or BS; following lines
will line up until you change the margin again.
--Note that the editor also AUTO-CAPITALIZEs for you. On
each line, all letters are capitalized except between
comment braces {...} or between quotes '...' or "..." . This
makes your program statements easily distinguishable from
comments with no work on your part.
MOVING the CURSOR.
There are several ways to move the cursor around in your
file. The left, right, up, and down arrows are all you
really need, but other keys like PGUP (page up) and PGDN
(page down) make larger moves and are handy. CTRL-left arrow
and CTRL-right arrow (or END) move the cursor to the start
and end of the current line, respectively.
--Note that if you move the cursor or type past the right
edge of the screen, the editor scrolls right to keep the
cursor on the screen; lines that are partially off-screen to
the left are clearly marked. Use CTRL-left arrow to return
to the 1st column position; the right portion of the line
(past the edge of the screen) will also be cleared marked.
--If pressing the cursor-arrow keys puts numbers into you
file, instead of moving the cursor, you much press
Ctrl-NumLock to activate the cursor control function keys.
DELETING and MOVING text.
You can backspace (BS) back over text; or, move the cursor
to the letter to remove and press DEL. Hold it down for
longer deletions.
To delete 1 or more entire lines, use the cut and paste keys
F5, F6, and F7. F5 marks the line where the cursor is,
highlighting it. Move the cursor up or down to mark more
lines.
F5 pressed again finishes marking text and puts a copy of it
in a special copy buffer; the word 'TEXT' on the status line
tells you a copy has been stored.
F6 deletes the marked lines. Now, if you wish, you can move
the cursor elsewhere and press F7 to put a copy back into
the text. It's hard to make a serious mistake since each
time you delete lines, you can always copy them back if you
want!
To delete one line, just press F5-F5-F6.
That's all you need for now. See the EXTRAS chapter for
commands that make your editing even easier, such as:
1. search for words and change them if you want;
2. find a line by number;
3. delete words or part of a line;
4. switch between files;
5. move text between files;
6. print parts of your file;
7. center your work on the screen.
