Lesson 7: Multiple Buffers

      You may remember the word "buffer" from Lesson 3, when we
learned how to read and write files from the text buffer.  As you
recall, we said that the buffer was a place for storing the text
while we manipulated it, and that files were copied into it and
replaced from it.

      Perfect Writer has more than one buffer for manipulating
text.  This can be handy when you are working on several files at
once.  For example, this training manual is made up of several
lessons, and if we wanted to edit two or three of them, making
changes to one based upon the others, it would be nice to be able
to read them all into Perfect Writer at the same time.  Each file
we choose to use could be read into one of Perfect Writer's
buffers.

      Look at the mode line at the bottom of the screen.  Notice
the portion that says "lesson7: lesson7".  In the mode line,
"lesson7" is the buffer name.  Since we have multiple buffers for
storing text, they must be named in some way, just like files or
disc drives.  Buffer names may be from one to eight characters
long.  "lesson7" is the one you get automatically when you start
Perfect Writer up.  Each of these buffers of text also has a
filename associated with it.  In this case, the filename is
"lesson7".  We talked about filenames in Lesson 3.

      There is a command which will list on the screen what
buffers of text currently exist.  This command is C--X C--B, the
"Buffers Directory" command.    Try it now.   Type:
	  C--X C--B  

You should see a display at the top of the screen, overwriting
whatever text was there before.  The text is not gone, just
momentarily not displayed; this is an exception to the rule that
what you see on the screen is what is in your document.  Take a
quick look at the display line with the buffer list on it.  It
has the name, "name", and the file name, "lesson7", and a number,
which tells you how many characters are in the buffer of text. 
Type a C--L now to redisplay the screen.  The buffer list has
been replaced by the original text again.

      There is a command to create a new buffer, the C--X B
command.  It stands for "Switch Buffers", and looks similar to
the C--X C--B command, so you can remember them both fairly
easily. Try this command now.  Type:

      C--X B 

Perfect Writer will ask you for the name of a buffer to use, by
displaying a message in the echo line.  Type in the name "other",
followed by a carriage-return.  Perfect Writer will ask you if
you want to create a new text buffer.  We do, so type a "Y" to
answer yes.  Now the screen is devoid of text.  Look at the mode
line, and notice that the buffer name is now "other".  We moved
into a brand new text buffer, which has no characters in it. 
Notice also that the filename in the mode line associated with
this buffer is called "NAME.ME".  This is so that if you
mistakenly type a C--X C--W command to write the file without
giving a filename, the text will be stored in a conspicuously
named file.  Type a few characters just so the buffer isn't
empty.

      Now type a C--X C--B again to see a new list of the text
buffers.  Notice that the list now shows two buffers.  Going to a
new text buffer did not delete the old one; it is just waiting
for whenever you want to go back to it.  Do that now; type:
	   C--X B  name  <CR>

The Lesson 7 text will appear again.  Note that C--X B didn't ask
you if you wanted to create a new buffer, because one by that
name already existed.  Type the C--X C--B command again, to list
the buffers.  Notice that there is an asterisk beside the "other"
buffer.  This means the same thing as the star on the mode line
does: the text buffer hasn't been written out to a file since it
has been modified.

      Now go to another new buffer, called "lesson5".  Type:

      C--X B

Perfect Writer responds in the echo line:  "Switch to Buffer [CR]: "

      Enter:  lesson5 [CR]  (The "Y" is in answer to the question
asking if we want to create a new buffer.)  Now that you're in
the "lesson5" buffer, read in the file containing Lesson 5. 
Type:

      C--X C--R  lesson5  <CR>

The text will appear (if you got the file name right) and the
mode line will now have a section saying "lesson5: lesson5". Type
a C--X C--B again to get a buffer directory listing, if you like.

      It is usually quite useful to have the buffer name be the
same as the first half of the file name which Perfect Writer
uses.  We just accomplished that by creating a buffer with a name
appropriate to the file we were about to read in.  But Perfect
Writer can do this automatically for us.  The command C--X C--F
(for "Find File") will read in a file, in the same manner as C--X
C--R, but will automatically create a buffer of the appropriate
name for it.  Try it now.  Type:

      C--X C--F

	Perfect Writer will respond:  "File to Read [CR]:"

      Enter:  lesson4  <CR>

The mode line will now say "lesson4: lesson4", and the text of
Lesson 4 should be on the screen.

      The C--X C--F Find File command does just a little more
than automatically selecting a "nice" buffer name.  It will look
through all the Perfect Writer buffers you have to see if the
file you want to find has already been read into a text buffer
before.  If so, it just switches to that buffer, rather than
creating a new one and reading in the file.  This is usually what
you want; if you had made changes to a buffer containing a file
and then did a Find File, you would want to see the modified
version. Try it now.  Type:

      C--X C--F  lesson5  <CR>

Note that this puts you back in the "lesson5" buffer.  Try:

      C--X C--F  name.me  <CR>

This puts you into the buffer called "other", with its original
file name.  So, C--X C--F always does an automatic C--X B command
for you, either to a buffer which contains the file name you
want, or to a new buffer into which it reads the file.  It
effectively prevents you from ever having to remember whether of
not you had read in a file.  Just use C--X C--F all the time.

      With all these buffers it would useful to be able to view
more than one buffer at a time.  Perfect Writer has a split
screen feature which allows you to view the contents of two
buffers simultaneously.  This feature allows you to compare the
contents of separate buffers on the same screen.  The split
screen is created by the "Two Window" command C--X 2.  When you
enter this command the screen is divided into 2 parts with a line
across the middle.  When this command is given the screen will be
divided into two windows but both windows will contain the same
buffer, with the cursor in the top window.   Give the Two Window
command now.  Enter:

	C--X 2

You can switch the cursor from the top window to the bottom
window with the Other Window command "C--X O {the letter O stands
for Other}.  Do that now, go to the Other window on the buffer by
entering: C--X O  {Enter the letter 'o'}

The cursor has now switched to the other window.  The value of
the split-screen feature is that it allows you to see two
different buffers on the screen at the same time.  So lets read a
different buffer into this bottom window with the Find File
command, C--X C--F.  Begin by listing the Buffer Directory. 
Enter:

	C--X  C--B

This provides a directory of current file buffers.  Read a
different file into the lower window with the Find File command,
C--X  C--F.  Let's read in file buffer "lesson4".  Type:

	C--X  C--F  lesson4  <CR>     

The "lesson4" buffer is now viewed in the bottom window while the
"other" buffer is viewed through the top window.  It is possible
to switch to the other buffer using the other buffer command,
C--X  O.  Do that now, type:   

	C--X  O

The cursor is now in the top window where the "other" buffer is
viewed.  It is possible to scroll through the bottom window,
while the cursor is in the top window, with the view Next Screen
(Other Window) command, C--X  C--V.  Try this command now, enter:
		
		C--X  C--V

The file in the bottom buffer has been moved or scrolled up one
screenful (which is now about 10 lines because the size of the
screen has been divided).  It is also possible to scroll back
down a screenful in the other window with the view Previous
Screen (Other Window) command, C--X  C--Z.  Use this command to
return the bottom screen to its original position, enter:  

		C--X  C--Z

The window on the bottom screen has returned to its original
position at the beginning of the file.  To return to the One
Window display, enter the One Window command, C--X 1.  Do that
now.  Enter:
		     C--X 1

The bottom screen display has been cleared and the full one
window screen is used for the current buffer file.

      Do a C--X C--B to see what text buffers and files you have
again.  There are certainly a lot of unneeded buffers, so let's
get rid of some of those old buffers.  The command to do this is
C--X K (for "Kill buffer").  Type:

      C--X K  lesson4  <CR>

This will delete the buffer called "lesson4", which contains the
file "lesson4".  Be sure to remember the difference between a
buffer and file.   C--X K and C--X B work with buffer names,
while C--X C--F, C--X C--R, and C--X C--W all work with file
names.  Do a C--X C--B again, and notice that the buffer named
"lesson4" is no longer there.  Now type:

	C--X  C--B 

	Then type:

	C--X  K  other  <CR>

This command is intended to delete the buffer called "other",
which just happens to be the one on your screen now.  Perfect
Writer will not delete a buffer which we are currently working
on, and so it asks us which buffer we would like to go to
instead.  Type "name" followed by a <carriage-return>, and
Perfect Writer will then switch you back to the "name" buffer
(which has the Lesson 7 text in it), and try to delete the
"other" buffer.

      But there is another message at the bottom of the screen:
Perfect Writer will ask you if you are sure that you want to kill
the buffer, because it has some text (those few characters) in it
which has not been written out to (i.e., saved on disk) since the
changes were made. (Remember the star in the C--X C--B listing
and at the right end of the mode line now?)  Answer "Y" for yes,
and let Perfect Writer delete the buffer.  You can check this out
with a C--X C--B listing if you like.

      What advantages does using several buffers have besides
allowing you to look at several files back and forth?  It allows
you to move or copy text from one buffer to the other as well. 
In Lesson 5, we used the delete region command (or C--W wiping or
M--W copying mechanism) to move or copy text from one place to
another in a file.  This method works on multiple files in
separate buffers as well.  You can delete text in one buffer, do
a C--X B command to another buffer, and Yankback the deleted text
in the new buffer.  If you are using the split screen feature
then you can delete text in one window, switch to the Other
Window, and Yankback the deleted text into the separate buffer in
the other window.

      Let's work through an entire example in detail.  This is a
chance for us to review some of the many commands that you have
learned in Lessons 5, 6, and 7.  The task is to take the first
paragraph of this text, Lesson 7, and make it the first paragraph
of Lesson 5.  The buffer which we are now in, "name", contains
the file "lesson7".  The other buffer, "lesson5", contains the
file "lesson5".

      (1) M--< to the beginning of lesson7.

      (2) C--N down to the first line of the paragraph.

      (3) M--Space or the Mark Set command your computer uses
	    to set the mark at the beginning of the first line.

      (4) M--N to get to the end of the paragraph.

      (5) C--W to wipe out the paragraph.

      (6) C--X 2 to create Two Windows.

      (7) C--X O to switch to Other buffer.

      (8) C--X B lesson5 <CR> to go to buffer "lesson5".
      
      (9) M--< to the beginning of that buffer.

      (10) C--N down to the line before the start of the first
	     paragraph.

      (11) C--Y to yank the text back.  It should now be the
           first paragraph of Lesson 5.

      (12) C--X 1  to see the results.

Don't forget that the text is still yankable again; you may want
to go back to the other buffer and copy it back in with a C--Y.

      We have learned some commands in this lesson which you
might not use quite at first.  Sooner or later, though, you will
be using them regularly.  If you get into the habit of using C--X
C--F to read in a file initially, you will find it easier to use
the multiple buffers later when you need to.  Experiment some
more with buffers and moving text back and forth among them using
the split screen display.  When you exit Perfect Writer with the
C--X C--C command, be sure NOT to write out the buffers, so that
Lessons 5 and 7 are intact for the next person to use them.

	This lesson concludes our series on the use of Perfect
Writer to edit text files (as well as computer programs).  You
are now ready to use a very powerful word processor.
 yank the text back.  It should now be the
           first paragraph of Lesson 5.

      (12) C--X 1