Linkers, Loaders and Software

Linkers  Loaders  Software

Linkers and Loaders:

Basic loaders functions, central loaders scheme, absolute loaders, Subroutine linkers, relocation loader, Direct linking loader, Dynamic linking loader,

Design of absolute loaders and direct linking loader

Software tools: Software tools for program development, editors, debug monitor, programming environment, user interfaces.

Software Tools for program Development

Software tools are used extensively for program development and user interfaces

• Editor
• Debug monitor
• Programming Environment
• User Interfaces

Editor

Editor is computer program that allows a user to create and revise target document

Document includes object as computer programs, text, equations, tables, diagrams, lines and photographs.

The document editing process is an interactive user-computer dialogue

1.Select the part  to view and manipulate
2.To determine the format of and display
3.Specify and execute operation

4.Update the view appropriately

Text editor are of following types

1. Line Editors
2. Sreen Editors
3. Word processors
4. Structure Editiors

Line Editors

• Text editor are of following types
• It is primitive form of editor
• User has to specify line to change text
• Interaction with the editors is through a set of commands , this makes a editor less user friendly
• E.g. VI editor, VIM editor

Screen Editors

• Screen editors enables to modify any text by moving cursor to desired location.
• This is very useful while formatting the text to produce printed document
• E.g. office document.

Word processor

• A word processor recognize word a basic entity
• It support spell check option
• It has following options

1.Moving a section of text from one place to another
2.Delecting a section of text
3.Searching a word
4.Merging of text
5.Replacement of word
6.Spell-Check

Structure Editors

• A structure editor has awareness of structure of document.
• A structure is specified by user while creating and modifying the document.
• E.g.   LatTex

Editor Structure

• Editing module is collection of module deling with editing tasks.
• Travelling module of editor performs the setting of the current editing and viewing pointers
• In viewing module start of the area to be view is determine by current viewing pointer

Debug Monitor

• Debug monitor provides following facilities

1. Setting breakpoints in the program
2. Initiating a debug conversation
3. Displaying values of variables
4. Assigning new values to variable

• Debugging system provides functions such as tracing and trackback.
• Tracking used to track the flow of execution logic and data modification
• Trackback can show path by which the current statement reached
• In debugging user specifies breakpoints and action to be performed

Programming Environment

• Programming environment is an integrated program development environment
• It has following facilities

1. Program creation
2. Editing
3. Execution
4. Testing and debugging

Programming Environment has following components 

     1. A syntax directed editor

     2.Compiler ,Interpreter

     3.Debug monitor

     4.Dialog monitor

User Interfaces

• A user interface plays an important role in simplifying the interaction of user with application
• UI functioning has two important aspects

1.  Issuing Commands
2.  Excange of data 

• The presentation manger is responsible for managing user’s screen and for accepting data
• The dialog manager is responsible for interpreting user command and implement them
• Dialog manger is also responsible for  error message

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