107. What is a sub theme in Drupal ?

Sub-themes are just like any other theme, with one difference: They inherit the parent theme's resources. There are no limits on the chaining capabilities connecting sub-themes to their parents. A sub-theme can be a child of another sub-theme, and it can be branched and organized however you see fit. This is what gives sub-themes great potential.

Read More https://www.drupal.org/node/225125

95. Drupal coding standards

Read Here https://drupal.org/coding-standards

93. Explain drupal advanced search

When Drupal does a search, and returns no results, an advanced search form is displayed. The form contains a list of content types and below fields.

1. Containing any of the words

2. Containing the phrase

3. Containing none of the words 
And users can choose the search criteria if they are not able to find what they want from basic search.

92. Drupal 8 , Changelog.txt - What's new in Drupal 8

Drupal 8.0, xxxx-xx-xx (development version)

----------------------

- Added Twig as the default template engine and converted all .tpl.php templates

  to .html.twig.

- Added tour module. Provides highly contextual tips for UI elements.

- Improved entity system.

    * Added support for saving and deleting entities through the controller.

    * Entities are now classed objects, implementing EntityInterface.

    * Drupal now understands the concept of a "default" revision, tracked

      independently from the latest revision, allowing for the creation of

      drafts while the current revision stays published.

    * All entity types, not just nodes, now have support for revisions.

- Replaced the core routing system with one built on the Symfony2 framework.

- Configuration:

    * Added a centralized file-based configuration system.

    * Allows module authors to provide configuration in a standard format.

    * Implements functionality to get, set, add and remove configuration.

    * Includes ability to override configuration values with language variants

      and other runtime values.

- Added the CKEditor WYSIWYG editor. Provides a drag-and-drop configuration UI.

- Included the HTML5 Shiv library to support HTML5 elements in IE 8 and below.

- Included the following Symfony2 components:

    * ClassLoader - PSR-0-compatible autoload routines.

    * DependencyInjection - Flexible dependency injection container.

    * EventDispatcher - Object-oriented lightweight event handling system.

    * HttpFoundation - Abstraction objects for HTTP requests and responses.

    * HttpKernel - Core system for managing incoming HTTP request and responses.

    * Process - Allows for executing commands in a sub-process.

    * Routing - Framework for mapping incoming requests to controller

      information.

    * Yaml - Parser for YAML files.

- Included the Assetic asset management framework for PHP.

- Included Backbone.js and Underscore.js JavaScript frameworks.

- Support added for making HTTP requests through a proxy server.

- Removed modules from core.

    * The following modules have been removed from core, because contributed

      modules with similar functionality are available:

      * Blog

      * Dashboard

      * OpenID

      * PHP Filter

      * Poll

      * Profile

      * Trigger

- Removed the Overlay module from core.

- Removed the Garland theme from core.

- Removed the Statistics module's accesslog functionality and reports from core.

- Removed backwards-compatibility with 'magic_quotes_gpc'/'magic_quotes_runtime'

  PHP configuration settings. Both are required to be disabled.

- Universally Unique IDentifier (UUID):

    * Support for generating and validating UUIDs.

- JavaScript changes:

    * Updated to jQuery 2.1.0

    * Updated to jQuery UI 1.10.2

    * Removed jquery.bbq

- Tremendously improved language support all around.

    * Great language improvements for users:

      * Improved language selection with user preference detection in the

        installer.

      * Moved base language support to Language module.

      * Greatly simplified the interface for setting up languages.

      * Improved browser language detection considerably.

      * Language domain and path prefix configuraton simplified and centralized;

        path prefix detection is now default.

      * Added HTML 5 language markup; language information added in markup in

        several more places.

      * Made it possible to assign external language codes to local languages.

      * Introduced the possibility of an administration-specific language

        preference for users.

    * Simplified and added new features in interface translation:

      * Made interface translation directly accessible from language list.

      * Centralized interface translation import to one directory.

      * Drupal can now be translated to English and English can be deleted.

      * Much improved built-in translation interface.

      * Added support for singular/plural discovery and translation.

      * Customized translations are tracked so your modifications can

        be identified and protected from translation update overwrites.

      * All Gettext files are now imported in chunks, better for low resource

        environments.

    * Improved content language support:

      * Made it possible to assign language to taxonomy terms, vocabularies,

        menu items, and files.

      * Added a field translation based content translation module that applies

        to all content entities.

      * Removed the old node-copy based content translation module.

      * Introduced language defaults configuration for each entity type and

        subtype.

      * Added entity language variance support to search module.

      * Search indexing and query preprocessors now get language information.

      * Unified content translation permission granularity with content editing

        permissions.

      * Made the language selector freely orderable in entity forms.

    * Better configuration language support

      * Added language selectors to most configuration options (views, menus,

        etc.)

      * Added a configuration translation user interface that works with any

        configuration with translatable values (blocks, views, fields, etc).

      * Added language options to block visibility.

    * Much improved language APIs for developers:

      * Added simple APIs and hooks to save/delete/update languages.

      * New Language class wraps language information, used universally.

      * Unified database schemas and APIs to make it easier to spot where

        language codes are referenced.

      * Made the language negotiation system APIs more consistent for

        developers.

      * Made it possible for users to have a preferred language separate from

        their user entity language.

      * The text formatter from t() is now available as format_string().

      * Added support for interface translation contexts in Drupal.t(),

        Drupal.formatPlural() as well as routing, tabs, actions, and contextual

        links.

      * Removed textgroups support from interface translation in favor of

        native configuration language support.

      * Added configuration schema system to support generating translation

        forms for any configuration.

      * Reworked Gettext PO support to use pluggable read/write handlers.

      * Added language select form element in the Form API.

- Added E-mail field type to core.

- Added Link field type to core.

- Added Phone number field type to core.

- Added local image input filter, to enable secure image posting.

- Added Views and Views UI module to core.

- Added Entity Reference field type to core.

- Added Date field type to core.

- Added a Web Services module package.

    * Added a RESTful web services provider module.

    * Added a serialization module using the Symfony serialization component.

    * Added a Hypertext Application Language (HAL) serialization module.

    * Added a HTTP Basic authentication provider module.

Source : // https://api.drupal.org/api/drupal/core%21CHANGELOG.txt/8

89. Drupal Version release dates

Release dates

1.0      15 Jan 2001

2.0       15 Mar 2001

3.0        15 Sep 2001

4.0       16 Jun 2002

4.5        16 Oct 2004

4.6       16 Apr 2005

4.7       16 May 2006

5.0      15 Jan 2007 

6.0      13 Feb 2008

7.0      5 Jan 2011

7.26    15 Jan 2014

8.0 Drupal 8 is in development, with no set release date yet. The work on Drupal 8 is divided into categories, called Core initiatives: Mobile, Layouts, Web Services, Configuration Management, and HTML5.

66. What is drupal region ?

Defined areas of a page where content can be placed. Basic regions include: Header, Footer, Content, Left sidebar, Right Sidebar. Different themes can define different regions so the options are often different per-site. Content is assigned to regions via blocks. They can be ordered by weight within regions to define the order in which they display.

65. What is permission in drupal ?

In Drupal, a tool for controlling access to content creation, modification and site administration at the application level. Administrators assign permissions to roles, then assign roles to users. The first user of a Drupal site (User1) automatically receives all permissions. In operating systems like UNIX, permissions are security settings restricting or allowing users to access information or perform certain functions at the operating system level. In the case of files on UNIX systems, there are three types of permissions: read, write and execute.