_text_Editor in system software.pptx.pdf
- 1. Module 6
- 2. 6.1.Text Editors: ⚫ 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.
- 3. ⚫ A text editor allows you to edit a text file (create, modify etc…). ⚫ For example, the Interactive text editors on ◦ Windows OS – Notepad, WordPad, Microsoft Word, ◦ UNIX OS - vi, emacs , jed, pico. ⚫ Normally, the common editing features associated with text editors are, ◦ Moving the cursor, Deleting, Replacing, Pasting, Searching, Searching and replacing, Saving and loading, etc.
- 4. 6.1.1Overview of the editing process ⚫ An interactive editor is a computer program that allows a user to create and revise a target document. ⚫ Document includes objects such as computer diagrams, text, equations tables, diagrams, line art, and photographs. ⚫ In text editors, character strings are the primary elements of the target text.
- 5. ⚫ Document-editing process in an interactive user-computer dialogue has four tasks: - ◦ 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
- 6. ⚫ The above task involves traveling, filtering and formatting. Editing phase involves – insert, delete, replace, move, copy, cut, paste, etc… Traveling – locate the area of interest Filtering - extracting the relevant subset Formatting – visible representation on a display screen
- 7. 6.1.2. User Interface: ⚫ Conceptual model of the editing system provides an easily understood abstraction of the target document and its elements. For example, ⚫ Line editors – In this, you can only edit one line at a time or an integral number of lines. You cannot have a free-flowing sequence of characters. It will take care of only one line. ⚫ Screen editors – In this type of editors, the user is able to see the cursor on the screen and can make a copy, cut, paste operation easily. It is very easy to use mouse pointer.
- 8. ⚫ The user interface is concerned with, the input devices, the output devices and, the interaction language. ◦ The input devices are used to enter elements of text being edited, to enter commands. ◦ The output devices, lets the user view the elements being edited and the results of the editing operations ◦ interaction language provides communication with the editor
- 9. ⚫ Input Devices are divided into three categories: ⚫ Text Devices are keyboard. ⚫ Button Devices are special function keys, symbols on the screen. ⚫ Locator Devices are mouse, data tablet. ⚫ There are voice input devices which translates spoken words to their textual equivalents.
- 10. 1. 2. Output Devices are ◦ Teletypewriters(first output devices), ◦ Glass teletypes (Cathode ray tube (CRT) technology), ◦ Advanced CRT terminals, ◦ TFT Monitors and Printers (Hard-copy). 3. The interaction language could be, typing oriented or text command oriented and menu-oriented user interface. ⚫ 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. ⚫ 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.
- 11. 6.1.3 Editor Structure: ⚫ Most text editors have a structure similar to that shown in the following figure. ⚫ That is most text editors have a structure similar to shown in the figure regardless of features and the computers ⚫ Command language Processor accepts command, uses semantic routines – performs functions such as editing and viewing. ⚫ The semantic routines involve traveling, editing, viewing and display functions.
- 13. ⚫ Editing operations are specified explicitly by the user and display operations are specified implicitly by the editor. ⚫ Traveling and viewing operations may be invoked either explicitly by the user or implicitly by the editing operations. ⚫ In editing a document, the start of the area to be edited is determined by the current editing pointer maintained by the editing component. ⚫ Editing component is a collection of modules dealing with editing tasks. ⚫ Current editing pointer can be set or reset due to next paragraph, next screen, cut paragraph, paste paragraph etc..,. ⚫ When editing command is issued, editing component invokes the editing filter – generates a new editing buffer – contains part of the document to be edited from current editing pointer. ⚫ Filtering and editing may be interleaved, with no explicit editor buffer being created.
- 14. ⚫ In viewing a document, the start of the area to be viewed is determined by the current viewing pointer maintained by the viewing component. ⚫ Viewing component is a collection of modules responsible for determining the next view. ⚫ Current viewing pointer can be set or reset as a result of previous editing operation. ⚫ When display needs to be updated, viewing component invokes the viewing filter – generates a new viewing buffer – contains part of the document to be viewed from current viewing pointer. ◦ In case of line editors – viewing buffer may contain the current line, Screen editors - viewing buffer contains a rectangular cutout of the quarter plane of the text. ⚫ Viewing buffer is then passed to the display component of the editor, which produces a display by mapping the buffer to a rectangular subset of the screen – called a window.
- 15. ⚫ The editing and viewing buffers can also be partially overlapped, or one may be completely contained in the other. ⚫ Windows typically cover entire screen or a rectangular portion of it. ⚫ May show different portions of the same file or portions of different file. ⚫ Inter-file editing operations are possible. ⚫ The components of the editor deal with a user document on two levels: In main memory and in the disk file system. ⚫ Loading an entire document into main memory may be infeasible – only part is loaded – demand paging is used – uses editor paging routines.