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CHAPTER 2
EDT BASICS
2.1 INTRODUCTION
The first chapter briefly surveyed EDT's features. You will use some
of those features when you first start editing with EDT. You can
learn about the other features as you need them.
This chapter describes basic EDT concepts and features. Because EDT
has so many features, including three primary editing modes, you do
not need all the information contained in this chapter before
beginning your first EDT session.
This chapter includes material for readers of all levels. If you have
had little or no experience with computer editors, you should not
expect to understand every detail. For example, when you read the
section about journal file recovery, you might not fully grasp
everything. But after a system interruption occurs and you see the
journal file in your directory, you can refer back to the journal
section to find out how to use this facility.
The first sections in this chapter cover some of the terminology and
concepts that you should be familiar with when using EDT. There is a
brief description of starting and ending an EDT editing session.
EDT's journal/recovery facility is the subject of the last section.
2.2 BASIC TERMINOLOGY AND CONCEPTS
In learning about EDT you should be aware of certain terms that are
used to describe the editor and its operations. Some of these terms,
such as string, file, and buffer, have the same meanings in other
computer applications. Others, such as mode and editing session, have
special meanings in the context of describing EDT.
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EDT BASICS
2.2.1 EDT Terminology
TERM DEFINITION
______________________________________________________________________
EDT An interactive text editor.
Mode Method of editing. EDT has three primary
editing modes: keypad, line, and nokeypad.
Screen Mode Either keypad or nokeypad mode. These modes
can only be used on certain types of screen
terminals. (See Appendix C for the list.)
Change Mode An editing mode that you access through line
mode's CHANGE or SET MODE CHANGE command.
Change modes are keypad, nokeypad, and a
secondary editing mode called hardcopy change
mode.
Keypad Mode The main screen mode. This mode uses the keys
located on the small keypad at the right of
the terminal keyboard to perform editing
functions. You can use this mode on VT100
type and VT52 terminals.
Nokeypad Mode A screen mode that uses command words and
abbreviations to perform editing operations.
These commands enable you to extend the keypad
mode operations through EDT's key definition
facility. You can use this mode on VT100 type
and VT52 terminals.
Line Mode An editing mode that can be used on any
command terminal connected to an operating
system that supports EDT. Line mode uses
commands to perform editing operations.
Hardcopy Change Mode A secondary editing mode that enables you to
use most nokeypad editing commands on
terminals not supported for screen editing.
Editing Session The work you do with the EDT editor from the
time you type the system EDIT/EDT command
until you type EDT's EXIT or QUIT command.
Insert State The way EDT behaves when you are inserting
text in line or nokeypad mode. For example,
pressing the RETURN key adds a line terminator
to your text instead of sending data to the
computer. Use CTRL/Z to exit from the insert
state.
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EDT BASICS
Operating System The underlying software that runs the computer
to which your terminal is connected. This
manual deals with EDT running on the TOPS-20
operating system.
Prompt The signal that you get from your operating
system or from EDT that tells you to type
commands or information at your terminal.
System Command Level When you see a system prompt (for example $ or
@), respond with a system command. If you are
at the system command level, you are not using
the EDT editor.
File A collection of data that is located in a
relatively permanent storage area in the
computer. You use EDT to create and edit text
files.
Text File A file that is composed of ASCII-type
characters such as letters, digits, and
punctuation marks.
Input File A file that contains text used by EDT at the
start of or during your editing session.
Output File A file that EDT creates and into which it puts
text.
File Specification A unique file identifier. File specifications
must include at least the file name, but can
also include device, and directory information
as well as file type and generation number.
Buffer A temporary storage area that you use during
your editing session.
Text Entity A group of one or more contiguous characters
that EDT considers as a special unit. Text
entities include: word, line, sentence, and
page.
Control Character A special character signal that affects
printing or device operations. To send the
signal to the computer, you must press both
the CTRL key and a keyboard key. Control
characters signal such printing operations as
end of line, end of page, and tab stop.
Control Key Sequence The combination of keys needed to produce a
control character. Control key sequences are
represented as CTRL/x where CTRL refers to the
CTRL key and "x" is a character on the
keyboard.
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EDT BASICS
Line Terminator The signal that tells the computer to start
the following text on a new line. In EDT you
can reference the line terminator with a
single character -- CTRL/M -- and insert a
line terminator in your text by pressing the
RETURN key.
Cursor An indicator that shows EDT's current position
in your text when you are using a screen mode.
Current Line The line where EDT is currently positioned in
line mode. In screen mode editing, the
current line is the one on which the cursor is
located.
Direction EDT's current direction. EDT works in two
directions -- forward toward the end or bottom
of the buffer and backward toward the
beginning or top of the buffer.
String A group of contiguous characters that you
supply with some EDT commands. You can use
strings for searching and substituting.
Select Range A group of contiguous characters (often
extending for several lines) that you want EDT
to operate on. For example, you can delete,
move, or copy a select range.
Line Number A number that EDT automatically assigns to a
line of text during your editing session.
These line numbers only appear when you are
working in line mode.
Line Range A reference to one or more lines that tells
EDT which part of the text you want the line
mode command to affect.
Specifier Information you supply with EDT commands to
tell EDT such things as how many times to
perform a command and which parts of the text
to affect. Text entities, counts, and line
ranges are specifiers.
Qualifier A special line mode command word that modifies
the way EDT performs the command. Qualifiers
are optional. Whenever you type a qualifier,
you must precede the qualifier word with a
slash (for example, /QUERY).
Default The option or setting that EDT uses when you
do not explicitly indicate otherwise.
2-4
EDT BASICS
2.2.2 Editing Modes
The editing mode you use with EDT depends on the type of terminal you
have and the nature of your editing work. If you have a VT100 type or
VT52 terminal, you can use screen mode. (See Appendix C for a list of
terminals that EDT supports in screen mode.)
You will want to focus your attention on keypad editing if you have
the appropriate terminal. As you become proficient in keypad mode,
you can increase the capabilities of keypad editing by creating
additional keypad key definitions. Since these definitions are based
on nokeypad command syntax, becoming familiar with nokeypad editing
helps you extend your keypad editing functions. Chapter 3 describes
keypad editing; Chapter 5 discusses nokeypad editing.
If you do not have access to one of these terminals, you must use line
mode. Chapter 4 describes line mode editing commands. Line mode
users can go directly to Chapter 4 after reading this chapter.
2.2.3 Editing Session
The term editing session or EDT session refers to the work you do at
your terminal from the time you issue the system EDIT command to start
editing with EDT until you give an EDT command to leave the editor.
Most sessions involve inserting, locating, moving, or deleting text.
For example, an EDT session might consist of asking EDT to create a
new file, typing text into it, correcting mistakes or making any
changes you want, and saving the results.
When you edit an existing file using EDT, you work on a copy of the
original file. The original file remains in its directory and is
unchanged by the editing work. EDT places the copy in a buffer where
you can edit the text. After you finish your editing session, you can
save a copy of the edited text in an output file or you can save
nothing. The contents of your original file are unaffected in either
case.
Whenever you ask EDT to edit a file that does not exist, the editor
sets up an empty buffer to hold the text you will be typing. You
still have the option of saving nothing when you finish your editing
session, since EDT does not actually create the new output file until
you end your session.
2-5
EDT BASICS
2.2.4 Prompts
In using EDT, you will see two types of prompts. One is the system
prompt. The system prompts are:
$
@
Whenever you see the system prompt, you are ready to type a system
command. The system command associated with EDT is:
EDIT
The |hand| symbol is used in this manual to represent the system
command prompt. When |hand| appears in an example, you should see one
of the normal system prompts at the left of your screen or paper:
|hand|EDIT
On most operating systems, EDT is the standard editor. To call up the
EDT editor, all you need to type is EDIT. However, if EDT is not the
standard editor on your system, you must include other system commands
to be sure of getting EDT instead of some other editor. The system
appendices give more information on explicitly invoking EDT.
There are a number of qualifiers that you can use with the EDIT
command. These system qualifiers enable you to do such things as
change the name of the output file, use the recovery facility, or
examine a file that you do not have the authority to modify. The
system appendices describe the qualifiers that you can use with the
EDIT command.
EDT has several prompts. The line mode prompt is the asterisk (*).
Whenever you see the asterisk at the left of your screen or paper, you
are ready to type a line mode command. The /QUERY qualifier in line
mode uses the question mark (?) as a prompt. Type one of /QUERY's
four valid responses when you see this prompt.
In keypad mode, EDT prompts you for a search string whenever you use
the FIND function. The prompt is the phrase "Search for: ". When
you use keypad's COMMAND function, EDT prints the prompt "Command: "
to tell you to type a line mode command.
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EDT BASICS
2.2.5 Files
A file is a collection of data that is treated as a distinct physical
unit. Files can contain a variety of data types, but EDT can work
only with text files. The type of material that is stored in text
files includes letters, memos, computer programs, lists, and tables.
The files are stored in the computer so that you can use them over and
over again.
Text files are composed of elements such as words and numbers. The
text elements are groups of characters that include letters, digits,
punctuation marks, and certain signal codes (for example, line
terminator, horizontal tab, and page separator). Appendix D lists all
the characters that are valid in text files.
Files that contain other computer codes or signals are not considered
to be text files and cannot be edited with EDT.
Some non-standard text files, such as those that have been processed
by the RUNOFF formatter, can be edited with EDT. You should be
careful when editing such files; you might not get the results you
expect. If possible, convert the files to standard text format before
editing them. If you cannot do this, you should be aware of which
elements make that file format non-standard. Try to avoid altering
those elements.
You can edit any text file that you have access to. If the file is in
your current directory, simply use the file specification with the
system EDIT command. For files in other directories, be sure to
include the directory specification in the EDIT command line.
When you give EDT the name of a file that does not exist in your
current directory or in the directory you specify, EDT prints the
message:
Input file does not exist
If you are using EDT to create a new file, this message confirms that
there is no file with that name. You can now enter the text you want
that file to contain. When you type the EXIT command at the end of
your session, EDT creates a file containing the text you typed.
If you expected EDT to find an existing file but received this
message, you have probably typed the wrong file specification or
forgotten to identify the directory. Use EDT's QUIT command to stop
the editing session and start over again with the system EDIT command.
2-7
EDT BASICS
2.2.6 Input And Output Files
EDT uses several files during an editing session. The term external
file refers to files outside of your editing session. These include
several types of input and output files.
Input files are files that already contain text that EDT uses to start
your editing session or that EDT adds to your editing session. When
you edit an existing file, that file is the primary input file. EDT
copies the text from that file into its MAIN buffer so you can edit
it.
A startup command file is another type of input file. EDT reads the
information contained in that file and processes it before turning
over the editing session to you.
During your editing session you can use the line mode INCLUDE command
to copy other files into your editing session. These files are also
input files.
Output files are those created by EDT at the end of or during your
editing session. The primary output file is the one that EDT creates
when you use the EXIT command to end your session. This output file
contains the copy of the text in your MAIN buffer.
Using line mode's WRITE or PRINT command you can create additional
output files during your editing session. These output files can
contain either the entire contents or a portion of any buffer. When
you type the file specification with the WRITE or PRINT command, EDT
creates that file either in the current directory or in another
directory if you include the directory specification in the command
line. Note, however, that you cannot create new directories with the
WRITE or PRINT command.
EDT's journal file is also an output file. EDT creates this file as
soon as you start your editing session and continues to add
information to it until the end of your session. However, in most
cases, when you end your session, EDT discards the journal file. (See
the last section in this chapter for more information on the journal
file.)
2.2.7 File Specification
You use the file specification to identify a specific file. A full
file specification can consist of five elements:
file name file type
device name directory name
generation number
On the TOPS-20 operating system, you can omit the generation number
whenever you want to edit the most recent generation of the file or
create a new file. Similarly, file specifications in some operating
2-8
EDT BASICS
systems do not have node names. If your operating system does use
node names, you can omit the node name whenever you are editing a file
on your local node.
Whenever you are required to use a file specification in an EDT or
system command, you must include at least the file name. The
remaining elements are optional. Most of the examples show both the
file name and the file type whenever a file specification is called
for.
2.2.8 Buffers
An EDT buffer resembles a file in that it occupies storage space in
the computer system and is used to contain text. However, the use of
that space is temporary. EDT buffers exist only for the duration of
your editing session. When you end your session, EDT discards all the
buffers you used.
The first thing EDT does when you start to edit an existing file is to
copy the text from that file into a buffer called MAIN. The original
file still exists in its directory; EDT works only on the copy. When
you use EDT to create a new file, the first thing the editor does is
set aside an empty buffer called MAIN. No new file actually exists
until you end your EDT session.
When you use the EXIT command to finish your editing session, EDT
copies the contents of the MAIN buffer into a new file. All the
buffers created during your session are deleted and the storage space
they occupied is turned over to the operating system for other uses.
Before you give the EXIT command, you can transfer the contents of any
other buffer to an external file by using line mode's WRITE command.
When you do not want to save a copy of the MAIN buffer, end your
session with the QUIT command.
In addition to establishing the MAIN buffer at the start of your
session, EDT also sets up another buffer called PASTE. EDT uses the
PASTE buffer for screen mode CUT and PASTE functions. Both the MAIN
and PASTE buffers are always part of your EDT session. You can delete
the contents of these buffers during your editing session, but you
cannot remove the buffers themselves.
You can create additional buffers to store pieces of text or
additional material that you might want to look at during your editing
session. Various line and nokeypad commands enable you to create new
buffers. Some line mode commands transfer EDT to the buffer that is
named in the command line. Whenever you see the buffer specifier
included in the command syntax for a line mode or nokeypad mode
command, you can use that command to create a new buffer.
Buffer names can contain any alphanumeric characters (letters and
digits, but not punctuation marks or control characters). However,
the name must begin with a letter. You can use one punctuation
character, the hyphen (-), in buffer names. If you like, you can
2-9
EDT BASICS
create a buffer name that has over 80 characters in it. But since you
will have to type the buffer name at least once, you will find short
names easier to use.
The SHOW BUFFER line mode command tells you the names of all buffers
that exist for your editing session and indicates the current buffer
with the equal sign (=). Line mode's CLEAR command can delete any
buffer that you no longer need except MAIN or PASTE. In the case of
MAIN or PASTE, the CLEAR command removes the contents of the buffer,
but does not discard the location. After you use the CLEAR command to
delete any other buffer, that buffer name no longers appears in the
SHOW BUFFER list.
You might become confused when specifying a buffer name in a line mode
command because EDT usually transfers you to the new buffer. If you
find yourself in an empty buffer, you might wonder what happened to
the text you were just editing. The SHOW BUFFER command not only
tells you the name of the buffer you are in, but shows you the names
of all the other buffers in your current EDT session and tells you how
many lines each contains. You can use this information to find your
way back to the buffer where you were working.
EDT has some special storage areas whose names never appear in the
SHOW BUFFER list because EDT maintains complete control over them.
You cannot specify these buffers in commands or enter them in any way.
However, you can influence the characters that are stored in them and
decide when or whether to insert their contents into your text. These
special buffers include the delete character buffer, the delete word
buffer, the delete line buffer, the search buffer, and the substitute
buffer. The three delete buffers are used only by the screen mode's
delete and undelete functions.
2.2.9 Text Entities
Text entities refer to specific elements of text that EDT recognizes
as units when you are working in a screen mode. These include
characters, words, lines, sentences, paragraphs, as well as the
beginning or end of these elements. Text entities are used in the
screen modes to move the cursor and to limit the extent of operations
such as deleting text. (A complete discussion of text entities
appears at the beginning of Chapter 5.)
In addition to helping you move the cursor, entities can be used to
determine how much text EDT will act on. You use entities with
functions that delete text, create select ranges, change the case of
letters, or reformat text by means of the FILL function so that EDT
knows which part of the text to work on.
You should be familiar with these entities when you start editing in a
screen mode:
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EDT BASICS
ENTITY DESCRIPTION
______________________________________________________________________
character Any single character: a letter, digit,
punctuation mark, or control character.
word A group of contiguous characters that are bounded
by spaces, ends of lines, tabs, or ends of pages.
line A group of contiguous characters that begins just
after a line terminator and ends with the next
line terminator.
sentence A group of contiguous characters that is bounded