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CHAPTER 6: ADVANCED EDITING.
HELP menus:
You can press ESC anytime to see a HELP screen that reviews the basic editing
commands. You can also press F1 from the HELP screen or while editing to use
the filing system menu to update a file, print parts of a file, switch to
another file, or stop editing.
MOVING the CURSOR -- on the line:
left or right arrow = move 1 character left or right;
End = move to end of this line;
Ctrl left/right arrow = move to start/end of line;
TAB, Shift-TAB = move to next/prev. TAB position;
F2, Shift-F2 = move to next/previous word;
MOVING the CURSOR -- up or down:
up or down arrow = move 1 line up or down;
PGUP/PGDN = move 20 lines up/down;
Ctrl-PGUP/PGDN = move to start/end of file;
F4 + linenumber = go to this line number in file;
Hint: you can use either F4 CR or Ctrl-PGUP to go to the start of the file
quickly.
Hint: also see SEARCHING for Text, another way to move around in the file.
Hint: the HOME key doesn't move the cursor in the file, but it places the line
with the cursor near the middle of your screen. It is handy when you are
entering text near the bottom of the screen and you want to look ahead a bit
as you go.
SEARCHING for text:
Searching starts with the character just after the cursor position. Press:
F3
and enter the text you are looking for. Upper and lower case don't matter.
Press CR to start the search. The message 'Ctrl-F3= Replace' or 'Not Found!'
will appear. To search for another occurrence of the same word, just press:
F3 CR.
Hint: to search for text starting from the beginning of the file, do this:
F4 CR
F3 text CR
Hint: you can edit or move around in the file and later search again for the
same word last searched with:
F3 CR
Hint: you can leave a place marker in the file, such as zzzz; later, to return
to this point, just search for it:
F3 zzzz CR
Searching for and Replacing text:
After searching for and finding some text, the message:
Ctrl-F3 = Replace
is shown. If you press Ctrl-F3, you will be asked what to replace the text
that you found with:
Replace with:_
You can type in whatever you want to replace the text you found. When you
press CR, the text is replaced, and you will be asked if you want to find
another occurrence of the text you found. If you answer 'Y', and another
occurrence is found, you will be asked if you want to replace this one also.
You can continue to find and replace many occurrences of the same text by
answering 'Y'; you can bypass and not change a particular occurrence of the
text by answering 'N' to the question: 'Replace this one?', and you can stop
searching for more occurrences by answering 'N' to the question: 'Find
Another?'.
ENTERING text.
TYPING inserts text, pushing the rest of the line over. You can move the
cursor past the actual end of a line (which is shown by a shadow-box
character). If you type out here, the line is automatically extended with
spaces. You can enter text anywhere on the screen without worrying about the
actual line length; the shadow-box is there just in case you want to know
where the actual end of a line is (some printers might be limited in line
width, for example).
Hint: END and Ctrl-right-arrow always move to the actual end of line; if your
cursor is past the end of line, it will move to the left in this case.
Hint: as described in THE BASICS, the editor capitalizes what you type
automatically. But if you don't like this, just press F8 to toggle this
feature on or off.
A NEW LINE is created by typing CR when the cursor is anywhere on a line. A
new line is started below, with the same left margin as its upper neighbor.
SPLITTING a LINE is done by putting the cursor on the character which is to
start the new (2nd) line, and pressing Ctrl-CR.
JOINING 2 LINES is done by putting the cursor on the 1st of the 2 lines to
join and pressing Ctrl-BS.
INDENTING is controlled by F9 and F10. F9(UNDENT) moves the margin of the
current line left by 2 spaces; F10(INDENT) moves the margin right 2 spaces. It
doesn't matter where the cursor is on the line when you use F9 or F10, so you
can move down a program, re-formatting it line by line, quite easily.
DELETING text.
BS deletes the character to the left of the cursor;
DEL deletes the character at the cursor;
Ctrl-F2 deletes a word (if the cursor is on a word) or
up to the next word (if not);
Ctrl-F4 deletes the rest of the current line;
Note that F9 (UNDENT) deletes leading spaces, and Ctrl-BS deletes the line
separator characters.
Deleting entire lines and blocks of lines is done with the cut and paste
commands.
CUT (Delete lines) and CUT & PASTE (Move lines).
As described in the BASICS chapter, you use:
F5 to start or end marking text, and move it to the
copy buffer;
F6 to cut (delete) the block you have just marked;
F7 to paste (copy) the text from the buffer to the
current location of the cursor.
Hint: the last text you put into the buffer stays there until you quit the
editor, so you can switch files and copy the text into the new one.
Warning: Each time you mark text, it becomes the only text in the copy buffer.
So if you are going to move text around, be sure to copy it into the program
BEFORE marking the next block of text (because the new block will over-write
the old block in the buffer).
Hint: in re-arranging text in a program, you can store pieces of text at the
end of the program, and later move them to a final location.
Hint: you can print the text that is in the buffer with the filing system (see
below).
THE FILING SYSTEM.
F1 brings the filing menu to the screen. The filing system allows you to
switch files, make backup copies of a program, print text, and quit the
editor, with the most common actions carried out by pressing CR. The commands
available are:
R to REPLACE (update) a file and RUN it;
Q to QUIT the editor;
B to BACKUP a file, using any name and any disk
drive;
S to SWITCH to another file;
P to PRINT marked text on the printer.
REPLACE means to update the same disk file you started editing with the
changes you made in the current editing session, and then compile and run the
same program.
QUIT means stop editing and leave the editor. If you have changed your file
at all since loading it, you will be asked if you are sure you want to quit.
BACKUP prompts you for the file name to write the edit file to. You can
specify any legal DOS filename, including a drive prefix, and even a full
pathname if you want. Afterwards, you stay in the editor, so you can use this
command to write an extra copy of your file to another disk, as a backup.
You can also select S for SWITCH FILES. The current file will be updated if it
has been modified, and you will be prompted for a new file name. Type the new
name and CR, and edit the new file. Note that the copy buffer is still intact,
so you can move blocks of text between files this way.
The 2nd time you select SWITCH FILES, the last file you edited will be the
default(suggested) file name, so you can switch between 2 files repeatedly
without entering their names more than once. This makes it easy to build a
new file from parts taken from other files. The editor keeps track of the line
you were on in each file.
Finally, you can select P for PRINT BUFFER to send the contents of the copy
buffer (the marked text) to the printer. Use this to print out portions of a
program for proofreading, etc.
Note: File names may include drives and extensions, like
a:myfile.txt
and may include sub-directory pathnames if you are using them. (If you are not
sure what these are, you aren't using them and don't worry about it!)
ERROR MESSAGES AND PROMPTS.
On the lowest screen line, to the right of 'Press ESC for HELP', is an area
used for messages to help you with some commands or warn you of errors that
have occurred.
First, an explanation of the serious errors:
WHAT FILE?? -- the file name you have typed is not a valid PC-DOS file
name; check your spelling and try again.
FILE TOO LARGE! -- if you try to edit a file that is too large for the
editor or your computer's memory, the edit is cancelled after this message. If
you edit a file containing TAB characters, the editor converts these to spaces
and the file could possibly grow too large during this conversion, with the
same result.
TOO MANY LINES! -- if you try to edit a file with over 3000 lines, the edit
is cancelled with this message.
DISK ERROR!! -- this message occurs when attempting to update a file if
the drive's door is open, or the disk has too little room on it for the file,
or no room in its directory. An additional message is also given to indicate
what you should do. Generally, you must fix the problem (switch disks, etc)
and try again. When you get this error, you have not updated your disk file
yet! Try to do it before quitting the editor, or you will lose the editing you
have been doing.
CHECK PRINTER! -- this means that your printer is off, or off-line, or
otherwise not properly connected or functioning. Fix the problem and re-try
the print command.
LINE TOO LONG! -- this means that you have tried to make a line longer
than 250 characters; the editor can't do this, and you probably didn't want to
do it either!
Del. all lines? -- this message is given if you try to delete the entire
file with the cut command (F6). The editor assumes that you don't want to do
this.
Block too large. -- given if you try to mark too large a block of text for
your copy buffer. This can only happen with computers that have 128K of memory
or less.
Messages that are less serious and more for guidance are:
Low on memory! -- you are within 1000 characters of the maximum file size
you can edit.
NEW FILE! -- the file with the name you typed was not found on the
disk, so the editor assumes you will type in text for a new file of that name.
Of course, you might have misspelled the file name, so the editor beeps (in
case you are not looking!).
Converting tabs. -- the editor found TAB characters in your file and is
expanding them into spaces at intervals of 8 columns.
LONG lines split -- the file you are editing had lines longer than 250
characters in it, and these lines have been split. This editor is not intended
for editing files, such as word processor output, with lines this long,
although in a pinch you can split the lines up as you like with Ctrl-CR.
Writing... -- the editor is writing a file to disk after an UPDATE
command was given.
Written. -- the UPDATE operation is complete.
Autocaps is on.
Autocaps is off. -- these tell state of the auto-capitalization feature.
Scrolling right. -- the screen is moving right, following the cursor, and
the left-most screen column is no longer column 1 of your file. To return to
the left-most 'standard' position, you can use Ctrl-left arrow or ESC-ESC.
Printing... -- printing of the copy buffer is in progress.
Searching... -- a search command is in progress.
Ctrl-F3 = Replace -- a search has found what you wanted; you may, if you
like, replace it with text you specify by pressing Ctrl-F3 and following the
prompts.
Not found! -- a search did not find what you wanted. Note that the
search command starts just after the current cursor position, so you may need
to return to the beginning of the file before searching to find every
occurrence of the text you want.
Marking... -- you pressed F5 once. Move the cursor to mark the text
you want, then press F5 again.
Text in buffer. -- you pressed F5 again, and the text you marked has been
copied into the copy buffer. The word TEXT appears on the next-to-last screen
line as a reminder.
Text deleted. -- you pressed F6 and the marked text has been removed.
goto marked text -- you pressed F6 but the cursor was not in the marked
text. You can only delete text while the cursor is in the block, so move the
cursor into it and try again.
mark text first -- you pressed F6 but either you had not marked some text
first OR you have done some line-editing since marking the lines. The editor
only allows you to delete text BEFORE adding or deleting lines anywhere in the
file.
No text to copy. -- you pressed F7 but there is nothing in the copy buffer
to copy into the file.
Text copied. -- you pressed F7 and text was copied from the copy buffer
into the file.
TECHNICAL SPECS FOR THE EDITOR
The editor will run on computers which are compatible with the IBM-PC to the
extent of having the same screen memory addresses. This includes all IBM
models plus most 'close' compatibles. Dos 2.0 or later is required. BIOS
functions are used for cursor and screen mode control; MS-DOS functions are
used for keyboard input and all disk and printer I/O. 40 column screens can be
used as well as 80. Full Dos 2.0 pathnames can be used for the edited files.
Files to be edited must use CR,LF pairs to separate lines. TAB characters in
the file will be expanded to spaces; no other characters will be converted,
and 'strange' characters in the file will be displayed in the standard IBM
character set. Only characters from 32 to 126 ASCII can be entered into files.
The maximum line length is 250 characters; longer lines are broken when the
file is loaded if necessary. There is an absolute limit of 3000 lines per
file.
The editor makes use of what memory is available in the computer to create an
edit buffer and a copy buffer. In a 128K machine, the edit buffer will be
about 60,000 characters, and the copy buffer will be about 10,000. In a larger
machine, the copy buffer will expand to 60,000 characters. In a 64K machine,
both the edit and copy buffers will be small, about 5000 characters.
The editor is named VISED.EXE as distributed; a batch file EDIT.BAT is used to
edit VISIBLE-PASCAL files and controls the filing system command to compile
and Run the program. The batch file places a '/' after the program file name:
VISED demofile/
and this enables the Replace and Run filing option.
When used with the companion compiler, the editor will locate errors in the
source file automatically. This is done by entering the edit file with '/e'
after the filename:
VISED demofile/e
The editor then inspects BIOS RAM locations for information concerning the
line, column, and number of the error that occurred. An error file named
ERR.TXT is opened, if present, and the correct error message is read form it
and displayed right below the portion of the source file where the error
occurred.
However it is entered, using the 'R' command exits the editor with an exitcode
of 1, which can be read by a .BAT file to decide what to do next. Since the
exitcode from the 'Q' exit command is 0, the file RUN.BAT which controls the
system ends if the exitcode is 0, and starts the compile and run process if
the exitcode is 1.
SUMMARY OF CURSOR MOTION COMMANDS
cursor-arrow-keys move 1 character up, down, left,
right;
Ctrl-left-arrow go to start of line;
Ctrl-right-arrow go to end of line;
End go to end of line;
PgUp, PgDn move up or down 20 lines;
Ctrl-PgUp, Ctrl-PgDn go to start, end of file;
SUMMARY OF EDITING KEY COMMANDS
Esc look at help menu;
Home place the current line near the
screen center;
Del delete the character over the
cursor;
BS (backspace) delete the character to left of
cursor;
CR start a new line below the
current one;
Ctrl-CR split the line at the cursor
location;
Ctrl-BS join the current line with the
next one.
SUMMARY OF FUNCTION KEY OPERATIONS
F1 go to filing system to update,
run, quit, switch files, or
print parts of a file;
F2 move right one word;
Shift-F2 move left one word;
Ctrl-F2 delete a word or delete up to
next word;
F3 ____ search for text and optionally
replace it;
Ctrl-F3 replace text (after finding it
with F3);
F4 ____ go to line ____. F4 CR = go to
line 1;
Ctrl-F4 delete from the cursor to the end
of line;
F5 mark the start or end of a block
of text;
F6 delete the marked block of text;
F7 copy last block marked to the
cursor location;
F8 toggle auto-capitalization on or
off;
F9 move the margin left two spaces;
F10 move the margin right two spaces.
SUMMARY OF FILING SYSTEM COMMANDS
R (after EDIT file) Replace a Visible-Pascal file and
Run it;
R (after VISED file) Replace file and quit editing;
Q Quit editing;
B Backup to a file with any drive
and name;
S Switch to another file;
P Print the marked text on the
printer.
CHAPTER 7: RUNNING VISIBLE-PASCAL PROGRAMS
To RUN a program you use the part of the Visible-Pascal system called the
DEBUGGER -- it helps you find and fix program bugs, or errors. You use it by
issuing the command 'RUN myfile' or by using 'EDIT myfile' and selecting
'R' from the editor's filing system menu. The debugger allows you to watch
the operation of the program as it runs, to see whether it does what you want
it to. The debugger allows you to step through a program, one statement at a
time, while watching the program listing to see what statement is being
executed, and what the values of program variables are. It also allows you to
control how fast the program runs and when it should stop, and allows you to
look at the output of the program (if it writes or draws on the screen) as
well as the information made available by the debugger. Using it is automatic;
the Visible-Pascal compiler creates program files which, when 'fed into' the
debugger, automatically make the 'connections' required for all the above to
happen.
Chapters 2 and 3 tells how to run a program using the debugger. Using these
quick introductions, try running a program or two to get the feel of how it
operates, and experiment with some of the commands. Then read this chapter,
which will describe each of the functions of the debugger in full.
The Program and Debugger screens
When a program runs it often uses the computer screen to write text or draw
graphics. You will want to watch this output as the program runs, to see what
it is doing. However, there is other information about a program which can be
useful, including a listing of the statements as they execute, the values of
program variables, etc. which can also help tell you what your program is
doing. The program output and the debugger's information about the program
would both ideally have separate screens for display. However, since you
probably only have one computer display, Visible-Pascal manages the
information coming from the program and the debugger so that you can watch
whichever one you want. A command to switch screens is used to view either the
program or the debugger output, and Visible-Pascal makes sure that 1) the
debugger information is always accurate, and 2) the program output is always
accurate and complete, with nothing lost during the times that you are
watching the debugger screen. In this way, the two kinds of information can be
viewed as separate windows on the computer screen. Pressing 'S' is the command
to switch to the other screen.
Looking at the values of variables
The debugger screen shows a copy (or LISTING) of your program, and looks a lot
like the screen looks when you are editing, except for a window at the bottom
with summaries of the debugger commands, and some information which is
inserted into the listing. The most important of this is the value of all
program variables, which is placed between angle brackets on the same line
with any variable declaration, like this:
YOUR_NAME : STRING; <<Harrold>>
COUNT : INTEGER; <<15>>
The variable COUNT has the value 15 at the moment, and YOUR_NAME is Harrold.
All variables except arrays have their current values right in the listing
like this. Local variables also have values if the procedure in which they are
declared is being executed. To see the values of variables that are 'off
screen', you can use the editing commands (such as PgUp, etc) to look around
in the listing. The Home key returns you to the line which is next to execute.
The debugger will try to place the variable values at the end of the line with
the declaration; if the line is very long, they will be crowded to the right
and may overwrite part of your program line. Leave more space (by putting
comments on a separate line) if you want to improve the appearance of the
program listing in the debugger.
Controlling program execution
There are several ways to use the debugger to control the execution of your
program. One way is to press 'R' for RUN: you will see the program run at
full speed, with the program output on the screen. This is essentially like
running without the debugger, except that you can always stop the program and
return to the debugger to look at variables or single step, etc. To stop a
program that is running, just press Ctrl-Break. The program will be stopped
and the debugger screen shown. You can switch screens between the program and
debugger output with the 'S' key, or do any other command (to be discussed
soon).
The Debugger Commands
R = RUN until BREAK or Checkpoint.
The RUN command always puts the program output on the screen and starts the
program running at full speed. It continues until one of four things happen:
1. You press Ctrl-Break;
2. The checkpoint line is reached;
3. An error occurs while the program is running;
4. The program finishes normally.
Except for the last case, the result is the same: the program is stopped, the
debugger is brought to the screen, and you can continue with any available
command. The checkpoint line is a line you have selected for the program to
stop at; it is discussed below under 'set checkpoint'. If the program stops
because of an error, you will be told the reason, and can look around in the
program to inspect variables; but the program cannot be re-started from the
point of the error. You must re-run it from the beginning.
<space> = do 1 line.
Pressing the space bar causes the program to execute one statement and stop.
This is often called 'single stepping' a program, and lets you follow what it
does as slowly as you like. You can inspect variables at any time. If you have
some doubt about what your program is doing, single stepping will show you the
sorry truth! If you have lots of time, it is the only debugging command you
need; other commands are actually time-savers, allowing you to mix some
full-speed execution with single stepping.
You can single step with either the debugger on the screen (to see the lines
of the program as they execute) or with the program output on the screen. You
can switch screens (with the 'S' command) to the screen you want, then single
step with <space>. Switch screens any time you like.
If you single step at a line with a READ or READLN statement, then if the
debugger is showing, you will be clearly told that the program is asking for
input, and you will be prompted to type it in. Single step the program WORDS
to see this in action. If the program output is on the screen, then your
program should prompt you for some input, and as you press <space>, you will
see the cursor move to the right for each space. This is the time to type in
the information your program is expecting. Try this with the WORDS program,
too.
N = Next line down.
The Next line command is a short-cut. If you are stepping through some
statements and you don't want to follow a procedure call statement into a new
procedure, but want to go to the next line in the procedure you are in, then
press 'N' instead of <space>. 'N' will also complete statements like:
FOR COUNT := 1 TO 5 DO WRITELN('something');
in one operation, whereas <space> would stop once for each time the WRITELN is
executed. Therefore, use 'N' to go to the Next program line after the current
one, no matter what the current line is.
W = watch the program execute slowly.
Watching a program means to execute each statement at a rate of about 1
statement per second, showing you the result on either the debugger or the
program screen. It is good for either automatically showing you the progress
of the program, or just to run a program in super-slo-mo. You can stop the
program anytime with Ctrl-Break, as always.
S = Switch to/from program screen.
'S' switches between the debugger screen and the program output screen. It is
a good habit to form to switch screens as a program runs, so you can see what
it is producing. When you are watching the debugger, all the output from the
program is captured and saved until you switch to the program screen; then all
the saved output is sent to the screen rapidly. It is possible to save more
information than will fit in memory, in which case some program output will be
lost. This won't happen if you occasionally switch screens as you debug the
program (and in any event, you usually have room for several screens full of
output in the buffer).
Ins = set, Del = clear the checkpoint.
You can set a checkpoint on a program line, which will cause the program to
stop and return to the debugger screen when that line is executed. It is used
when you want the program to execute at full speed up to a point which you
want to examine in greater detail (by single stepping, etc). To do this, just
use the cursor keys (up and down arrow, PgUp/PgDn, etc) to move the brackets
< > in the left margin of the listing to the line where you want the program
to stop. Then press Ins to insert the checkpoint there. A '!' will appear
inside the brackets: <!>. There is only one checkpoint at a time, so any
previous one set will be cleared. If you want to clear the checkpoint without
setting one, press Del at any time. After setting a checkpoint, you can
return to the current line by pressing Home. Now if you RUN or WATCH the
program, it will stop at the checkpoint line. Of course, if the program never
executes the line with the checkpoint, then it won't stop there!
Hint: If you put a checkpoint on the last line in the listing, the program
will stop after it is done, allowing you to check the final program screen and
any interesting program variables.
Cursor control keys.
To look around in the program and read the listing, or to inspect variables,
or to insert a checkpoint, you can use the cursor control keys that cause up
and down motion: up and down arrow, PgUp, PgDn, Ctrl-PgUp, Ctrl-PgDn, and
Home. They have the same meaning as in the editor, except that Home returns
you to the current line that is ready to execute. The left and right motion
keys don't do anything; if a long program line is partly off screen right,
there is no way to read the rest of it while in the debugger (although you can
return to the editor to do so). If the program is very large, the longer
lines in the listing may be abbreviated to save memory for the program.
Q = Quit, E = Edit : leaving the debugger.
If your program executes correctly and completely, it will end and the
debugger will exit, like any program would. But you can stop the debugger in
two other ways: 'Q' just stops, so you can do something else, or perhaps
re-run the program from the beginning; and 'E' goes directly to the editor,
and in fact directly to the line you are on, so you can fix the program and
re-run it. During the development of a program, you will find it convenient to
run, trace, or step the program until an error becomes apparent, then use 'E'
to exit directly to the editor, fix the error, and then select 'R' = RUN from
the filing system menu in the editor to re-run the program. You can repeat
the edit & run process quickly and easily until your program is perfect!
SUMMARY OF DEBUGGER COMMANDS
R Run program until <Break> or checkpoint;
<space> Run 1 statement and stop;
N run to the Next lower line and stop;
W Watch the program run slowly;
S Switch between debugger and program
screen;
Ins,Del Insert and Delete the checkpoint;
E go directly to the Editor;
Q Quit the debugger, return to DOS;
up/down arrow
PgUp/PgDn
Ctrl-PgUp/PgDn look around in listing; move < > for
setting the checkpoint <!>.
CHAPTER 8: VISIBLE-PASCAL SYNTAX
This chapter is to help you understand the limitations and special features of
Visible-Pascal; it isn't a complete Pascal manual or study course.
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. Therefore, an easy editor, fast and automatic program
execution and running, and a full symbolic debugger with the program operation
and variable values easily visible have been supplied at the expense of other
possible programming features. For example, Visible-Pascal is not a complete
implementation of Pascal; it does not generate programs that run as fast as
possible; and it does not include such advanced features as low level machine
access and modular program construction and linking. It is an adequate
language to allow the writing of interesting and significant programs,
however. Disk files can be read and written; strings are included; and the
various screen modes possible on the IBM-PC can be used, including the drawing
of graphics in color. All these features are fully supported by the debugger.
This chapter will describe some of the significant features of Visible-Pascal;
the supplied demonstration programs also have useful examples of various
features.
Pascal Language Features Included & Excluded
Visible-Pascal includes the following data types:
INTEGER 1, 32000, -55
BOOLEAN TRUE, FALSE
CHAR 'a', CHR(65)
STRING 'this is a string'
Enumerated (MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY)
TEXT files with integer, boolean, character, or string
components
Missing is the real data type. Variables can be both global and local; types
can be declared in a TYPE section, and used in variable declarations or in
parameter lists.
Single-dimensioned arrays with positive indexes are included:
ARRAY[1..10] OF INTEGER
ARRAY[1..100] OF CHAR
ARRAY[1..1000] OF BOOLEAN
Four text files are pre-declared:
INPUT = standard keyboard input, redirectable
OUTPUT = standard screen output, also redirectable
CON = screen output, not redirectable
PRN = printer output
Re-entrant use of procedure and functions is OK, but they cannot be declared
FORWARD nor are local procedures allowed. Full parameter passing is allowed,
by value or by address (VAR - parameters).
These Pascal control statement types are included:
IF...THEN...
IF...THEN...ELSE...
REPEAT...UNTIL...
WHILE...DO...
FOR...TO/DOWNTO...DO...
CASE...OF......END
But the GOTO statement is specifically excluded, as encouraging bad habits!
Set constants are included, so you can write:
IF X IN ['A'..'Z'] THEN...
but set variables are not included.
Records, pointers, and dynamic memory allocation are not included.
The following string procedures and functions are built-in:
CHR(int) returns character value of int
ORD(ch) returns integer value of char. ch
LENGTH(str):INTEGER returns the length of str
POS(str1,str2):INTEGER returns the position of str2 in
str1
CONCAT(str1,str2) concatenates str2 to str1
COPY(str1,str2,pos,cnt) copies str2[pos]..str2[pos+cnt]
to str1
DELETE(str,pos,num) deletes num chars at str[pos]
INSERT(str1,pos,str2) inserts str2 at str1[pos]
All strings have a maximum length of 80 characters, and a dynamic length of 0
to 80 which is stored as element 0. Thus, to set the length of S, do:
S[0] := CHR(LEN); if LEN is the length to set S to.
The following additional routines can be used for direct keyboard input:
KEYPRESSED:BOOLEAN is true if a key was pressed and
its value is waiting in the
keyboard buffer
INKEY:CHAR function returning the next key
from keyboard.
Returns keys immediately, without
waiting for
CR; also returns extended
(double) codes for function keys
and other special cases.
The following routines are supplied to control the screen:
CLS clears the screen, homes the
cursor
CURSOR(X,Y) sets cursor position. upper left
= 0,0
SETMODE(M) sets screen mode to one of the
following:
0 = black&white, 40 columns;
1 = color, 40 columns;
2 = black&white, 80 columns;
3 = color, 80 columns;
4 = 320x200 color graphics
5 = 320x200 black&white graphics
6 = 640x200 black&white graphics
7 = monochrome display adapter
TEXTTYPE(T) sets all characters following to
attribute:
0 = normal white on black;
1 = bold intensity
4 = underlined (monochrome
adapter only)
5 = blinking
7 = reverse video
8 = invisible
TEXTCOLOR(C) sets following characters to
color:
0 = black
1 = blue
2 = green
3 = cyan
4 = red
5 = magenta
6 = yellow
7 = white
TEXTBACKGR(C) sets the background color as
above
BORDER(C) sets the border color to colors
0..7, or
to colors 8..15 which are light
versions
PALETTE(X) Graphics only, selects palette 0
or 1
BACKGROUND(X) graphics only, selects color
0..15 as background
This routine is supplied for sound production:
TONE(NOTE,DURATION) makes a NOTE of DURATION msec.
NOTE is 1..15.
This routine is supplied to draw graphics on the screen:
DRAW(X1,Y1,X2,Y2,COLOR) draws a line from x1,y1 to x2,y2
in COLOR
An Outline of a Visible-Pascal Program
The following model program will show some of the basic structural parts of a
Visible-Pascal program.
PROGRAM DEMO; {no program parameters are needed}
CONST (* this is an alternative comment form *)
INTCONST = 1;
BOOLCONST = TRUE;
CHARCONST = 'x';
CHARCONST2 = "y"; {either ' or " can be used for quotes}
STRINGCONST = 'this is a string constant';
TYPE
ATYPE = ARRAY[1..100] OF INTEGER; {only positive indexes}
VAR
A,B,C : INTEGER; {you can do multiple definitions, but}
D : ATYPE; {it's not neat}
S1 : STRING;
F1 : TEXT; {the file type declaration}
PROCEDURE COUNTEMUP(INVAL:INTEGER;
VAR OUT:INTEGER);
{note value parameter for input and VAR parameter for output}
VAR {note local variable with same name as global}
D : BOOLEAN;
BEGIN
D := INVAL > 6;
IF D THEN OUT := 12 ELSE OUT := INVAL;
END;
FUNCTION ANOTHER:INTEGER; {a function returning an integer}
BEGIN
ANOTHER := ORD(INKEY); {built-in proc., gives next key}
END; { from keyboard (a char) }
BEGIN {this is the start of the program itself}
A := 1;
B := 2;
COUNTEMUP(A+B, C); {note expression for the value parameter}
WRITELN(C);
A := ANOTHER;
COUNTEMUP(A+C, C);
WRITELN(C);
WRITELN('all done now');
WRITELN("that's all, folks!"); {note use of ' or " }
END.
Syntax of Visible-Pascal
Identifiers in Visible-Pascal consist of the normal alphanumeric characters,
plus the underline character _ which is legal inside identifiers for improved
readability. Identifiers can be any length, but must differ from other
identifiers in the program in the first 10 characters. Numbers are normal
decimal numbers or hexadecimal numbers which are formed by using the dollar
sign as a prefix: $F000 for example. Comments are formed by pairs of braces
{...} or these alternates: (* ... *). You can put one kind of comment
around text that includes the other kind. String quotes can be put in either
single or double quotes (' or "), and the alternate type of quote can be
included in the string (see the last statement of the example above). The
editor automatically capitalizes characters typed except when they are within
single or double quotes or comment braces. Note that the alternate comment
form (* ... *) does not affect capitalization; for neat programs, use the {
... } form for normal comments, and the alternate form to 'comment out' a
procedure or region of the program temporarily.
A Visible-Pascal program consists of a PROGRAM statement, a declarations
section which consists of any number of CONST, TYPE, and VAR sections,
followed by any number of PROCEDUREs or FUNCTIONs, followed by the main
program part: a BEGIN ... END block, finally ended with a period. There are no
compiler directives, pseudo-comments, or other complications.
A PROCEDURE or FUNCTION consists of the heading, including an optional
parameter list, and, in the case of a function, a return type, followed by a
declarations section and a BEGIN ... END block finally ended with a semicolon.
Procedures cannot be nested inside other procedures. Function return values
must be simple types: INTEGER, CHAR, BOOLEAN, or enumerated, but not arrays,
strings, or files. See the demonstration programs for examples of various
procedures and functions.
Statements follow the syntax of standard Pascal closely. The CASE statement
also allows ranges of case labels to be expressed just like a set:
CASE X OF
1..5: STATEMENT1;
6..10: STATEMENT2;
END;
and their is no OTHERWISE clause in the case statement, as in some Pascals.
You should test for legal values of the case selector before the case
statement, unless you wish the run-time error trapping to report it for you!
Arrays are restricted to a single dimension, and thus an array of STRING is
not possible. In addition, the array index cannot be negative; all arrays
start with element 0 and go up to the maximum you declare (the minimum array
bounds that you specify is ignored).
There is no GOTO statement, since it encourages bad habits!
RESERVED AND PREDECLARED WORDS IN VISIBLE-PASCAL
The following words are keywords in the language, and must not be re-declared
by the programmer.
AND ARRAY BEGIN BOOLEAN CASE CHAR CHR CONST
DO DOWNTO ELSE END FOR FUNCTION GOTO
IF IN INTEGER MOD NOT OF OR ORD
PRED PROCEDURE READ READLN REPEAT STRING SUCC
TEXT THEN TO TYPE UNTIL VAR WHILE WRITE
WRITELN
There are two predeclared constants: TRUE, and FALSE.
There are four predeclared files: INPUT, OUTPUT, CON, PRN.
The following are built-in functions:
EOF EOLN ODD KEYPRESSED INKEY LENGTH POS
CHR ORD PRED SUCC
The following are built-in procedures:
ASSIGN RESET REWRITE CLOSE CLS CURSOR DRAW TONE
CONCAT COPY DELETE INSERT SETMODE TEXTTYPE TEXTCOLOR
TEXTBACKGR BORDER PALETTE BACKGROUND
Operators are:
+ - * / MOD
AND OR NOT IN
CHAPTER 9: TECHNICAL DETAILS AND INSTALLATION
Visible-Pascal consists of three major programs: VISED, VISBUG, and VISPAS,
which do the editing, debugging, and compiling functions of the Visible-Pascal
system. They are fairly small disk files (20-25K), but need considerable
memory for internal buffers and so require computers with 128K total memory.
Visible-Pascal is actually run using some batch (.BAT) files to control the
sequence of execution of the three major parts. For example, the EDIT command
executes the EDIT.BAT command file, which executes the editor, and then
depending on a return code which the editor gives back to the operating system
either executes the RUN batch file or simply stops. The EDIT.BAT file is:
echo off (this prevents display of the commands)
cls (clears the screen)
vised %1/ (edits the file, with / added to command line
if errorlevel 1 run %1 (Run the program if return = 1, else
quit)
The command to use to edit a non-Visible-Pascal file, such as this
documentation, is simply:
VISED manual.1
this uses the editor directly.
The RUN.BAT file also uses return codes to control execution. The following
notes will help to understand it.
-VISPAS uses standard input and output for the source and code (.COM)
files;
-VISPAS returns errorlevel 5 if a fatal error occurred (such as
program too long), and errorlevel 1 if a syntax error was
found;
-VISBUG, the debugger, returns errorlevel 1 if the editor is
requested, and 0 to just quit;
-If Vised is entered with /e on command line, a syntax error will
be displayed as the first edit screen.
-After a succesful compilation, a .COM file is left on the disk,
and the program can be executed without the debugger's aids; for
example, to execute WORDS directly, type:
WORDS <CR>
INSTALLATION
Programs generated by Visible-Pascal use standard DOS operations for input and
output in all cases except graphics drawing, changing screen modes, and making
sound. To do standard DOS I/O, a program called ANSI.SYS which is supplied
with DOS must be used when the computer is started or reset. The steps
required to do this are:
1. Remember to start the computer with a DOS 2.0 or later
disk;
2. This disk must have the file ANSI.SYS on it;
3. This disk must also have a file called CONFIG.SYS on
it;
4. CONFIG.SYS must have the line:
DEVICE=ANSI.SYS
included in it (it can have other lines if your system
requires).
If all the Visible-Pascal files on are this boot disk, then the supplied
AUTOEXEC.BAT file will cause the execution of the batch file G.BAT which will
give a sign on message to Visible-Pascal and a directory display, after which
you are off and running. A separate disk can be used for Visible-Pascal; just
insert it in the default drive and type G.
CHAPTER 10: DEMONSTRATION PROGRAMS
SOUNDS -the first program to try
WORDS -another introductory program
TURTLE -a simple program to draw on the screen
PRETTY2 -a prettyprinter (neatens your programs)
BOX -draws boxes
SOUNDS2 -a program that makes noise
PATTERN -controls cursor position and text attributes
COLOR -allows you to set screen mode and text color
STRINGS -shows the use of the INSERT string procedure
FILEDEMO -writes, then reads a disk file
INKEY -shows how to read keys, including function keys
TESTCASE -brief program to test CASE error trapping
LISTER -creates a listing with line numbers
WEATHER -uses boolean function to answer questions
MATH -a trivial 4-function calculator
KEYDFINE -program to re-define any key on keyboard
etc.(there may be more, soon)
CHAPTER 11: PRETTY-PRINTING
Sometimes your program has lost its nicely indented appearance, due to a lot
of editing changes, and while it is easy to use the indent and undent commands
in the editor to fix it up, there is a program supplied with Visible-Pascal
that does this for you, if you prefer. PRETTY1 is a program which reads a
file, which should be a valid Pascal program, and creates another file which
has been neatly indented and auto-capitalized. To use it to neaten up a file
called 'myfile', you would do:
PRETTY1 <myfile >newfile
The arrows are the commands for using standard input and output under DOS 2.0.
Done this way, a file called 'newfile' will be created and will be the
neatened version of 'myfile', which is not changed by the process. If you
want, you can then copy newfile to myfile and then erase newfile. Note that
using standard output can be useful; you could, for example, do:
PRETTY1 <myfile >prn
in which case the neatened file goes directly to the printer. Do not,
however, make the input file and the output file the same! Dust will fly if
you do...
PRETTY2 is the text of a program which can be RUN by Visible-Pascal. You can
customize this program if you want a different format for your programs. The
use of standard input and output is not compatible with stepping the program
with the debugger, so at the first debugger menu, Quit; then type:
PRETTY2 <myfile >newfile
to run the program without the debugger. If you just type
PRETTY2
you will have to type in the program, line by line; as you do so, each line
will be re-typed with the correct indenting on the screen. Type F6 CR to send
and end-of-file to the program.
CHAPTER 12: KEYBOARD RE-DEFINITION
If you don't like the way certain keys are used, in the Visible-Pascal editor
or in many other programs, you can fix things to your liking with programs
like KEYDFINE, a demonstration program which re-defines the Ctrl-A key to mean
' := ' , a key sequence you use a lot in Pascal. The IBM technical manual has
a chapter on using extended screen and keyboard control, which gives some
hints on how to do this. For now, RUN KEYDFINE; press 'R' at the debugger
menu. Now try pressing Ctrl-A and see what prints on the screen.
You can define any key to be any sequence of characters or other keys, and you
could make a second program that reversed, or undid, the actions of the first,
allowing you to re-define keys when using one program, but not changing the
key definitions permanently.
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