TEACH BUFFERS Revised: A. Sloman Oct 1987
MOVING AROUND FROM ONE FILE TO ANOTHER IN VED
=============================================
This file assumes you have already worked through TEACH TEACH and that
you know how to move the cursor around the window, how to make the
window move up or down the file you are looking at using the SCREENUP
and SCREENDOWN keys, how to insert and delete text in a file, etc. You
should also read TEACH VED before this one, to find out how to create
files of your own, quit files, save them on the magnetic disc etc.
You should by now have learnt how to switch between two files using
<ESC> x. If you don't remember how to do it read TEACH SWITCHWINDOW,
i.e. do:
<ENTER> teach switchwindow <RETURN>
Use <ENTER> q
to "quit" that file when you have finished.
Occasionally when you are developing programs you will find that you
have more than two files 'on the boil'. To be more precise, there will
be temporary copies of the files stored in the editor VED, and for each
one VED will remember how far you have got, what changes you have made
so far, etc.
But it is not possible (unless you have a very large screen with lots of
lines) to see more than TWO of the files at a time. This can make things
difficult, since the key-sequence <ESC> x will only switch you back and
forth between two files. If there is a third file, how can you get at
it?
One way is to ask for it by name - the same way as you originally got it
into the editor. E.g. to get this file you had to do: teach buffers. You
can always get this file back on the screen by doing:
<ENTER> teach buffers
To prove that, get two more teach files onto the screen, using the
following command
<ENTER> teach window
That will get TEACH WINDOW onto the screen and put the cursor into it,
then do:
<ENTER> teach switchwindow
That will put another TEACH file on the screen obscuring this one. You
can then do
<ENTER> teach buffers
That will put this file back in view.
Whenever a file is brought back into view by an ENTER TEACH command or
an ENTER VED command, it leaves the previous file visible. So if the
previous file was in the upper half of the screen the new file will be
in the lower half of the screen. This can seem a little confusing, as
files will not necessarily re-appear where you last saw them if you have
more than three files on the go.
Try using <ENTER> teach commands like those above to switch from one
teach file to another. Move the cursor to different places each time,
and notice how whe you go back to a file VED remembers where you were.
However if you QUIT a teach file, using ENTER q, then if you go back to
it with an ENTER teach command VED will put you at the beginning of the
file. Try that with TEACH WINDOW. I.e. go to the file, move to the end
of the file, then 'quit' it with ENTER q, then use
ENTER teach window
to get back to it. You'll see that the cursor is put at the beginning of
the file.
NOTE: this file is called TEACH BUFFERS because we use the word 'buffer'
as a jargon word to refer to the temporary copy of a file which VED
creates when you are editing the file. There isn't really much obvious
connection between this use of the word and its ordinary meaning: e.g.
it has nothing to do with railway buffers or buffer states. However, it
is now common in computing jargon to use the word 'buffer' to refer to a
temporary store of information.
Thus when you are editing six files using VED we say that there are six
buffers in VED.
-- QUITTING A FILE WITH ENTER q --------------------------------------
If you use ENTER teach to read a teach file, then that creates an extra
buffer in VED. That buffer will stay there until you either log out, or
tell VED that you want to 'Quit' that file by getting the file onto the
screen (as explained below) then typing ENTER q. ENTER q will always
immediately get rid of a teach file from VED (though the permanent
version will remain on the disk.) However if you use ENTER q on one of
your own files VED will first check whether you have done anything to
change the buffer. If you have, then before it lets you quit VED makes
sure that you really meant to.
To get a taste of that create a new file called junk1 with the command
ENTER ved junk1
(use some other name if you already have a file with that name). Then
type some rubbish in the file. Then try ENTER q. VED checks whether you
want the file stored on disc. You can press the N key to quit without
saving the file.
NB. If you have more than two files in VED then at most two of them can
be visible at once. Although the others are temporarily invisible, the
buffers still exist: VED keeps detailed records in the computer's
temporary memory. So the disappearance from the screen doesn't always
mean the buffer has gone. However when you QUIT a file, using ENTER q
then there is no longer any buffer for that file in VED. An earlier
version may still exist on the disk, however, so that you can look at it
later. But any changes you have made during the current session will not
be recorded if you've Quit the file and answered 'n' when asked if VED
should write it.
-- SWITCHING BETWEEN YOUR OWN AND TEACH FILES -------------------------------
Just as you can do
ENTER teach <name>
to go to a teach file called <name> , so you can use
ENTER ved <name>
to go to a file of your own called <name>. To get some practice at doing
this try the following. Read the next set of instructions up to the row
of asterisks and make a note of what you have to do, since by the time
you are half way through, the instructions will no longer be on the
screen (though you can always get them back on the screen by ENTER teach
buffers).
-- SWITCHING BETWEEN YOUR OWN FILES -----------------------------------
Read down to the row of asterisks before you try out the suggestions in
this section.
Create a new file of your own called TEST1 by giving the command
ENTER ved test1
Then type into it something like 'This is my file called TEST1' Create a
new file of your own called TEST2 by giving the command
ENTER ved test2
Then type into it something like 'This is my file called TEST2' (That
file will cover up these instructions.) Create a new file of your own
called TEST3 by giving the command
ENTER ved test3
Then type into it something like 'This is my file called TEST3' (That
file will cover up your TEST1 file.) Try switching back to your TEST1
file by means of the command
ENTER ved test1
Switch to each of the other files, TEST2 and TEST3, in turn. Return to
this file with the command
ENTER teach buffers
(Actually 'ENTER teach' alone will do, as VED remembers which teach file
you were on - i.e. teach buffers - as long as you have not quit the file
with ENTER q)
Now return to the last of your own files, with the command
ENTER ved
(If you don't give ENTER VED a file name, it assumes you want the same
file you last looked at, other than teach files. However it will not
take you back to a file which you have QUIT with ENTER q.) (Why not?)
Now return to this file using
ENTER teach
Make sure you have a good idea what's going to happen when you go
through those steps.
*************************NOW TRY DOING ALL THAT*************************
-- USING ESC e TO FIND OUT WHAT BUFFERS YOU HAVE -----------------------
The commands you have so far learnt will enable you to get to any file
you want at any time. However, if you have been working on lots of
files, you can easily forget which files are in the editor. You can ask
VED to give you a list of the names of files currently being looked at
with the <ESC> e command. I.e.
Press: <ESC>
Type: e
For each file it will print out the name of the file, and an associated
number. You can then press the key corresponding to the number to get
that file on the screen.
If you are only looking at one file, it will say so and go 'beep'. Try
<ESC> e, and see what it prints on the command line. If you have only
this file in VED, first get another file in, e.g. ved junk. To come back
to this file press the number corresponding to 'buffers' (the name of
this teach file).
Try using <ESC> e to switch from one file to another by pressing
different numbers. The last file you were editing is always No 1. The
one you looked at before that is No 2. etc. That is, every time you get
a file onto the screen it is brought to the front of the list.
If you end up with so many files that their names will not appear on the
command line, <ESC> e will create a temporary file and show you the
names in that. Then, as before you can select your file by pressing the
appropriate number. But you are unlikely to get that many files going at
once, unless you have been using VED for some time.
Before you finish with this file you should cycle through all your
'junk' files (if you created any, as suggested above) and do ENTER q in
them, to stop them being stored on the disk when you log out, wasting
disk space.
-- REVISION QUESTIONS --------------------------------------------------
You should be keeping a file (called 'vednotes') with a summary of
things you have learnt, or at least making notes using pencil and paper.
Add what you've learnt about switching files to your notes. In
particular note the answers to the following questions:
What is a buffer?
What does ESC x do? (See TEACH SWITCHWINDOW)
What does ENTER q do?
How does ENTER q treat a teach file differently from your own file?
What options does ENTER q give you if you try to quit a file of your
own after inserting or deleting some characters?
What happens if you type 'y' after the quit command?
If you are looking at one of your files, how can you get back to the
last teach file you were looking at?
If you are looking at a teach file, how can you get back to the last
of your own files you were looking at?
If you want to get back to one of your files called TEST2, and you
are not sure that it was the last one you were looking at, how
can you get back to it?
If you want to get back to TEACH WINDOW and it wasn't the last teach
file you were looking at, how can you get back to it?
How can you find out which VED buffers are currently in the
temporary store?
If you've made changes to a file and you want them stored on the
disk, what command should you give?
What does <ESC> e do?
What number does <ESC> e give to the last file you were looking at?
What is the difference between <ESC> w and <ENTER> w ?
(See TEACH VED for <ENTER> w)
Suitable teach files to look at next if you have not already seen them:
TEACH VED, TEACH MOREVED, TEACH MARK, TEACH VEDPOP
CONTENTS OF THIS FILE
- (Use <ENTER> g to access required sections)
-- QUITTING A FILE WITH ENTER q
-- SWITCHING BETWEEN YOUR OWN AND TEACH FILES
-- SWITCHING BETWEEN YOUR OWN FILES
-- USING ESC e TO FIND OUT WHAT BUFFERS YOU HAVE
-- REVISION QUESTIONS
--- C.all/teach/buffers ------------------------------------------------
--- Copyright University of Sussex 1987. All rights reserved. ----------