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The Command line interface was the first interactive dialog style to be commonly used and, in spite of the availability of a menu-driven interface, it is still widely used.

It provides a means of expressing instructions to the computer directly, using some function keys, single characters, abbreviations, or whole-word commands. Command line interfaces are powerful in that they offer direct access to system functionality, and can be combined to apply a number of tools to the same data.

They are also flexible: the command often has a number of options or parameters that will vary its behavior in some way, and it can be applied to many objects at once, making it useful for repetitive tasks. Menu In the menu-driven interface, the set of options available to the user is displayed on the screen and selected using the mouse, or numeric or alphabetic keys.

The options are: It is visible, less demanding on the user, and relies on perception rather than memory. However, menu options should still be useful, and grouped in a meaningful and logical way. recognize. Menus are often organized hierarchically and required options are It can be used at the top level of the hierarchy. The group and name of the menu options give users the only clue to find the option they need.

These systems can do any of the following: purely text-based, menu options presented as a numbered selection, or There is a graphical component where the menu appears rectangular box and the choice is probably Enter the first letter of your choice or corresponding entry go to the number or Menu with arrow keys.

This is a restricted form of a full WIMP system. Human-Computer Interaction Natural Language Perhaps the most attractive means of communicating with computers, at least at first glance, is by natural language.

Users unable to remember a command or lost in a hierarchy of menus may long for the computer that is able to understand instructions expressed in everyday words. Unfortunately, however, the ambiguity of natural language makes it very difficult for a machine to understand. Question/answer and query dialog Question and answer dialog is a simple mechanism for providing input to an application in a specific domain. The user is asked a series of questions and so is led through the interaction step by step. These interfaces are easy to learn and use, but are limited in functionality and power.

As such, they are appropriate for restricted domains and for novice or casual users. Query languages, on the other hand, are used to construct queries to retrieve information from a database.

They use natural-language-style phrases, but in fact require specific syntax, as well as knowledge of database structure. When asking questions, the user usually has to do this Specify one or more attributes to search the database and the attributes interesting to watch.

However, this is easy when there is a single attribute It gets complicated when multiple attributes are involved, especially if the user is interested in attribute A or attribute B, or attribute A and not attribute B, or where the values Attributes must be compared.