Text editor

 An Interactive text editor has become an
important part of almost any computing
environment
 Text editor acts as a primary interface to the
computer for all type of “knowledge workers” as
they compose, organize, study, and manipulate
computer-based information.
A text editor allows you to edit a text file (create,
modify etc…).
 The common editing features associated with
text editors are, Moving the cursor, Deleting,
Replacing, Pasting, Searching, Searching and
replacing, Saving and loading, and,
Miscellaneous(e.g. quitting)

 Windows OS - Notepad, WordPad, Microsoft
Word, and text editors.
 UNIX OS - vi, emacs, jed, pico.
 Gui based editors
• Gedit gvim
• Nedit
• Tea
• subtime

Overview of the editing process
 Document-editing process involves-
 - Select the part of the target document to be viewed
and manipulated
 - Determine how to format this view on-line and how to
display it
 - Specify and execute operations that modify the target
document
 - Update the view appropriately
O The above task involves traveling, filtering and
formatting. Editing phase involves
O – insert, delete, replace, move, copy, cut, paste, etc…
O - Traveling – locate the area of interest
O - Filtering - extracting the relevant subset
O - Formatting – visible representation on a display
screen

User Interface
O Conceptual model of the editing system provides
an easily understood abstraction of the target
document and its elements.
O Line editors – simulated the world of the key
punch – 80 characters, single line or an integral
number of lines,
O Screen editors – Document is represented as a
quarter-plane of text lines, unbounded both down
and to the right.
O The user interface is concerned with, the input
devices, the output devices and, the interaction
language.

O Input Devices are divided into three categories, text
devices, button devices and, locator devices.
O Text Devices are keyboard.
O Button Devices are special function keys, symbols
on the screen.
O Locator Devices are mouse, data tablet.
O voice input devices which translates spoken words
to their textual equivalents.
O Output Devices are Teletypewriters (first output
devices), Glass teletypes (Cathode ray tube (CRT)
technology), Advanced CRT terminals, TFT
Monitors
(Wysiwyg) and Printers (Hard-copy).

O The interaction language could be, typing
oriented or text command oriented and menu-
oriented user interface.
O Typing oriented or text command oriented
interaction was with oldest editors, in the form of
use of commands, use of function keys, control
keys
etc.,
O Menu-oriented user interface has menu with a
multiple choice set of text strings or icons.
Display area for text is limited. Menus can be
turned on or off.

Typical Editor Structure Diagram

Components of Editor Structure
OCommand language processor:
It accepts input from the user’s input devices, and
analyzes the tokens and syntactic structure of the
commands.
The command language functions much like the
lexical and syntactic phases of a complier.
In complier CLP may invoke semantic routines
directly.

In a text editor, these semantic routines perform
functions such as editing and viewing.
CLP may produce an intermediate representation
of the desired editing operations.
This intermediate representation is then decoded
by an interpreter that invokes the appropriate semantic
routines.
The use of an intermediate representation allows
the editor to provide the variety of user-interaction
languages with a single set of semantic routine.

The routines involves travelling, editing, viewing and display
functions.
OEditing operations are always specified explicitly by the user.
OThe Display operations are specified implicitly by the other
three categories of operations.
OThe travelling and viewing operations may be invoked either
explicitly by the user or implicitly by the editing operations
OThere is a relationship between this classes of operations
and it is considerably more complicated than a simple
model.

Simple relationship between editing and viewing
buffers

OIn editing a document, the start of the area to be edited is
determined by the editing component (which deals in
editing task).
OThe current editing pointer can be set or reset explicitly by
the user with traveling command such as…
ONext paragraph
ONext screen.
OOr implicitly by the system as a side effect such as delete
paragraph.
Current editing pointer

OThe traveling component of the editor actually performs the
setting of the current editing and the viewing pointers and
determines the point at which the viewing or editing filtering
begins.
OWhen the user issues an editing command the editing
component invokes the editing filter.
OThis filter generates a new editing buffer based on the
current editing pointer.

OThese parameters which are specified both by the user and
the system, provide information such as the range of the
text that can be affected by an operation.
--------------------End of CEP------------------

Current viewing pointer
OIn viewing a document, the start of the area to be viewed is
determined by the current viewing pointer.
OThis pointer is maintained by the viewing component of
the editor
OThe current viewing pointer can be set or reset explicitly
by the user with a travelling command or explicitly by the
system as a result of the previous editing operation .
OWhen the display needs to be updated, the viewing
component invoked the viewing filter.

OThis component filters the document to generate the new
viewing buffer based on the current viewing pointer as well
as on the viewing filter parameters.
OThis parameters which is specified both by the user and
system, provide information such as the number of
characters needed to fill the display and how to select them
from the document..
OThe editing and viewing buffers, while independent, can be
related in many ways. In the simplest case..
OThey are identical, the user edits the material directly on the
screen

Text editor

Recommended

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Text editor (20)

Recently uploaded (20)

Text editor