Friday, September 19, 2014

Daily Sevas

Description of Daily SevasSevas performed for the main deity
SuprabhatamTomala SevaArchana SevaEkanta SevaSevas performed for the utsava murthi
KalyanotsavamArjitha BrahmotsavamDolotsavam (Unjal Seva)Arjita VasanthotsavamSahasra Deepalankarana SevaSuprabhatam
'Suprabhatam' is the first and foremost pre-dawn seva performed in the temple of Lord Venkateswara. This ritual is performed at Sayana Mandapam inside sanctum sanctorum to wake up the Lord from His celestial sleep, amidst the rhythmic chanting of vedic hymns. Every day in the early hours acharyapurushas recite the hymns beginning with 'Kausalya Supraja Rama Purva Sandhya Pravarthathe’ in front of the main deity at Bangaru Vakili, while on the other hand, a descendant of Tallapaka Annamacharya sings some songs penned by the great saint poet in praise of Lord Venkateswara at the first corridor of the sanctum sanctorum at the same time.'Suprabhatam' is a Sanskrit term which literally means “Good Morning”. This particular hymn consists of four parts including Suprabhatam, Stotram, Prapatti and MangalasasanamSuprabhatam-It means awakening Lord from His divine sleep and it consists of 29 slokas.Stotram-These are the hymns in praise of Lord, consisting 11 slokas.Prapatti-Meaning total surrender to Lord and it has 16 stanzas.Mangalasasanam-It is the prayer sung in the glory of Lord consisting 14 stanzasThus, Suprabhatam, composed by Prativadi Bhayankara Annan, a disciple of the celebrated Vaishnava Preceptor, Manavala Mamuni consists of a total 70 slokas.This arjitha seva is performed before the Bangaru Vakili, after which the Bhoga Srinivasa Murthy(silver replica of the main deity and is also known as “Dhruva Beram”) who was laid to bed in the “Sayana Mantapa” is shifted back to “Garbha Griha” to commence His activities for the day. Archakas, jeeyangars, temple authorities and the Grihastha pilgrims who purchase tickets for Suprabhatam’, worship the Lord during this early morning seva and feel immense solace with the first glimpse of His Divine Charm that which cannot be described in mere words.Immediately after completing the 'Suprabhatam', Bangaru Vakili is kept open. The ritual lasts for over 30 minutes. (Suprabhata seva will not be performed in Dhanurmasa. Instead, 'Tiruppavai' is recited during this time.) The worship of Lord Venkateswara during Suprabhatam is considered highly meritorious. 'Suprabhata seva, tickets can be booked in advance.SRI VENKATESWARA SUPRABHATAM (with lyrics and meaning in English) Reporting Time:2:00 AMSeva Time:2:30 AMDay of Seva Performed:DailyPrice of a ticket (INR):120.00No.of Persons allowed:OnePrasadam / Bahumanam:2 small laddusNote : Children below 10 years are not allowed Suprabhatam stanzas, translation and audioThomala SevaThe word “Thomala” means a garland of flowers. Hence this arjitha seva assumes importance of decorating the presiding deity with exquisitely tied colourful floral and Tulasi garlands after awakening Him from celestial sleep with Suprabhata Seva.This arjitha seva is intended to call the special attention of the pilgrim grihasta who takes part paying requisite amount to witness the flower decoration of the “Mula Virat”(main deity)which takes place at the end of the puja.Known as “Thodutha Malai” in Tamil, the flower garlands in Yamunathurai are brought by the Periya Jiyar-the chief pontiff of Tirumala temple as per the traditional custom or by his Ekangi (disciple) in the temple, with a lighted torch in a procession to the rhythmic beat of Jeganta (handy bells)to the temple.The flower garlands are made into several pieces and each piece being of a particular size is adorned in the respective areas to enhance the Divine Beauty of Lord in a spectacular manner. This seva lasts for about 30 minutes. This arjitha seva is performed only on Tuesdays, Wednesdays and Thursdays while in Ekantam(pilgrims are not allowed)during the rest of the week.THOMALA SEVA DETAILS FOR GRIHASTAS:Reporting Time:3:00 AMSeva Time:3:30 AMDay of Seva Performed:Tue-Wed-ThuPrice of a Ticket (INR):220.00No.of Persons allowed:One Prasadam / Bahumanam:2 small laddus

Wednesday, September 17, 2014

12 Alwars

Hindu Temples » About 12 AlwarsAbout 12 Alwars

Alwars, who are said to be the Hamsam of Sriman Narayanan, have dedicated their lives towards the Emperumaan and they led their life by praising and doing Mangalasasanam on Sriman Naryanan. These Alwars are 12 in Number and out of which one is Sri Andal, who is a woman.

These Alwars were born in various parts of our country but they were all united in a common subject, ie dedicating their lives and praising the Lord.

Poigai Alwar, Bhoodath Alwar and Pei Alwar are collectively called as "Mudhal Alwars" were found in the same period of time.

Thirumazhisai Alwar, who thought the Perumal as his friend and has sung Mangalasasanam on Perumal.

Thirumangai Alwar, who was a great king in his starting of life but later, changed his life to work for the Perumal and for his bhaktaas.

Thondaradippodi Alwar, who is also named as "Vipra Narayanar" led his life as the slave to the Perumal and worked for the Perumal by dedicating him with Garlands.

Thiruppaan Alwar, who belonged to the Paanar family, praised the Perumal through his beautiful songs and Paasurams.

Periyalwar, is considered as the Mother, Father for Sri Andal and Father-in-Law to Perumal has sung Mangalasasanam on Perumal.

Sri Andal, who is also called as "Soodikkodutha Sudar Kodi" is said to be the daughter (brought up) of Periyalwar has created "Thiruppavai" in which she considers Sriman Naryanan as her husband. She is the only lady alwar.

Nammalwar, who sat below the Tamarind tree without having any food and sleep got Gnana and has sung Mangalasasanam on Perumal and he has worked hard to spread Sri Vaishnavam.

Madhurakavi Alwar, who is said to be the Sishyan (Student) of Nammalwar is also one among 12 Alwars.

Kulasekara Alwar, have a great bhakti towards Sri Ramar have also done Mangalasasanam on the Perumal particularly in Malayala Naatu thriuppathigal...

Tuesday, November 3, 2009

Interview Questions on ASP.NET

1. Describe the role of inetinfo.exe, aspnet_isapi.dll andaspnet_wp.exe in the page loading process.
inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things. When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe.

2. What’s the difference between Response.Write() andResponse.Output.Write()?
Response.Output.Write() allows you to write formatted output.

3. What methods are fired during the page load?
Init() - when the page is instantiated
Load() - when the page is loaded into server memory
PreRender() - the brief moment before the page is displayed to the user as HTML
Unload() - when page finishes loading.

4. When during the page processing cycle is ViewState available?
After the Init() and before the Page_Load(), or OnLoad() for a control.

5. What namespace does the Web page belong in the .NET Framework class hierarchy?
System.Web.UI.Page

6. Where do you store the information about the user’s locale?
System.Web.UI.Page.Culture

7. What’s the difference between Codebehind="MyCode.aspx.cs" andSrc="MyCode.aspx.cs"?
CodeBehind is relevant to Visual Studio.NET only.

8. What’s a bubbled event?
When you have a complex control, like DataGrid, writing an event processing routine for each object (cell, button, row, etc.) is quite tedious. The controls can bubble up their eventhandlers, allowing the main DataGrid event handler to take care of its constituents.

9. Suppose you want a certain ASP.NET function executed on MouseOver for a certain button. Where do you add an event handler?
Add an OnMouseOver attribute to the button. Example: btnSubmit.Attributes.Add("onmouseover","someClientCodeHere();");

10. What data types do the RangeValidator control support?
Integer, String, and Date.

11. Explain the differences between Server-side and Client-side code?
Server-side code executes on the server. Client-side code executes in the client's browser.

12. What type of code (server or client) is found in a Code-Behind class?
The answer is server-side code since code-behind is executed on the server. However, during the code-behind's execution on the server, it can render client-side code such as JavaScript to be processed in the clients browser. But just to be clear, code-behind executes on the server, thus making it server-side code.

13. Should user input data validation occur server-side or client-side? Why?
All user input data validation should occur on the server at a minimum. Additionally, client-side validation can be performed where deemed appropriate and feasable to provide a richer, more responsive experience for the user.

14. What is the difference between Server.Transfer and Response.Redirect? Why would I choose one over the other?
Server.Transfer transfers page processing from one page directly to the next page without making a round-trip back to the client's browser. This provides a faster response with a little less overhead on the server. Server.Transfer does not update the clients url history list or current url. Response.Redirect is used to redirect the user's browser to another page or site. This performas a trip back to the client where the client's browser is redirected to the new page. The user's browser history list is updated to reflect the new address.

15. Can you explain the difference between an ADO.NET Dataset and an ADO Recordset?
Valid answers are:
· A DataSet can represent an entire relational database in memory, complete with tables, relations, and views.
· A DataSet is designed to work without any continuing connection to the original data source.
· Data in a DataSet is bulk-loaded, rather than being loaded on demand.
· There's no concept of cursor types in a DataSet.
· DataSets have no current record pointer You can use For Each loops to move through the data.
· You can store many edits in a DataSet, and write them to the original data source in a single operation.
· Though the DataSet is universal, other objects in ADO.NET come in different versions for different data sources.

16. What is the Global.asax used for?
The Global.asax (including the Global.asax.cs file) is used to implement application and session level events.

17. What are the Application_Start and Session_Start subroutines used for?
This is where you can set the specific variables for the Application and Session objects.

18. Can you explain what inheritance is and an example of when you might use it?
When you want to inherit (use the functionality of) another class. Example: With a base class named Employee, a Manager class could be derived from the Employee base class.

19. Whats an assembly?
Assemblies are the building blocks of the .NET framework. Overview of assemblies from MSDN

20. Describe the difference between inline and code behind.
Inline code written along side the html in a page. Code-behind is code written in a separate file and referenced by the .aspx page.

21. Explain what a diffgram is, and a good use for one?
The DiffGram is one of the two XML formats that you can use to render DataSet object contents to XML. A good use is reading database data to an XML file to be sent to a Web Service.

22. Whats MSIL, and why should my developers need an appreciation of it if at all?
MSIL is the Microsoft Intermediate Language. All .NET compatible languages will get converted to MSIL. MSIL also allows the .NET Framework to JIT compile the assembly on the installed computer.

23. Which method do you invoke on the DataAdapter control to load your generated dataset with data?
The Fill() method.

24. Can you edit data in the Repeater control?
No, it just reads the information from its data source.

25. Which template must you provide, in order to display data in a Repeater control?
ItemTemplate.

26. How can you provide an alternating color scheme in a Repeater control?
Use the AlternatingItemTemplate.

27. What property must you set, and what method must you call in your code, in order to bind the data from a data source to the Repeater control?
You must set the DataSource property and call the DataBind method.

28. What base class do all Web Forms inherit from?
The Page class.

29. Name two properties common in every validation control?
ControlToValidate property and Text property.

30. Which property on a Combo Box do you set with a column name, prior to setting the DataSource, to display data in the combo box?
DataTextField property.

31. Which control would you use if you needed to make sure the values in two different controls matched?
CompareValidator control.

32. How many classes can a single .NET DLL contain?
It can contain many classes.


Web Service Questions

1. What is the transport protocol you use to call a Web service?
SOAP (Simple Object Access Protocol) is the preferred protocol.

2. True or False: A Web service can only be written in .NET?
False

3. What does WSDL stand for?
Web Services Description Language.

4. Where on the Internet would you look for Web services?
http://www.uddi.org

5. True or False: To test a Web service you must create a Windows application or Web application to consume this service?
False, the web service comes with a test page and it provides HTTP-GET method to test.


State Management Questions

1. What is ViewState?
ViewState allows the state of objects (serializable) to be stored in a hidden field on the page. ViewState is transported to the client and back to the server, and is not stored on the server or any other external source. ViewState is used the retain the state of server-side objects between postabacks.

2. What is the lifespan for items stored in ViewState?
Item stored in ViewState exist for the life of the current page. This includes postbacks (to the same page).

3. What does the "EnableViewState" property do? Why would I want it on or off?
It allows the page to save the users input on a form across postbacks. It saves the server-side values for a given control into ViewState, which is stored as a hidden value on the page before sending the page to the clients browser. When the page is posted back to the server the server control is recreated with the state stored in viewstate.

4. What are the different types of Session state management options available with ASP.NET?
ASP.NET provides In-Process and Out-of-Process state management. In-Process stores the session in memory on the web server. This requires the a "sticky-server" (or no load-balancing) so that the user is always reconnected to the same web server. Out-of-Process Session state management stores data in an external data source. The external data source may be either a SQL Server or a State Server service. Out-of-Process state management requires that all objects stored in session are serializable.

Thursday, September 3, 2009

DOTNET Framwork

.NET Framework 4.0:

Microsoft announced the .NET Framework 4.0 on 29 September 2008. The Public Beta was released on 20 May 2009. Some focuses of this release are:

* Parallel Extensions to improve support for parallel computing, which target multi-core or distributed systems. To this end, they plan to include technologies like PLINQ (Parallel LINQ), a parallel implementation of the LINQ engine, and Task Parallel Library, which exposes parallel constructs via method calls.
* Visual Basic and C# languages innovations such as statement lambdas, implicit line continuations, dynamic dispatch, named parameters, and optional parameters.
* Full support for IronPython, IronRuby, and F#.
* Support for a subset of the .NET Framework and ASP.NET with the "Server Core" variant of Windows Server 2008 R2.
* Support for Code Contracts.
* Inclusion of the Oslo modelling platform, along with the M programming language.

In 28 July 2009, a second release of the .NET Framework 4.0 beta was made available with experimental software transactional memory support. Whether this functionality will be available in the final version of the framework has not been confirmed.

In conjunction with .NET Framework 4.0, Microsoft will offer a set of enhancements, codenamed Dublin, for Windows Server 2008 application server capabilities. Dublin will extend IIS to be a "standard host" for applications that use either WCF or WF

.NET Framework 3.5:

Version 3.5 of the .NET Framework was released on 19 November 2007, but it is not included with Windows Server 2008. As with .NET Framework 3.0, version 3.5 uses the CLR of version 2.0. In addition, it installs .NET Framework 2.0 SP1, (installs .NET Framework 2.0 SP2 with 3.5 SP1) and .NET Framework 3.0 SP1 (installs .NET Framework 3.0 SP2 with 3.5 SP1), which adds some methods and properties to the BCL classes in version 2.0 which are required for version 3.5 features such as Language Integrated Query (LINQ). These changes do not affect applications written for version 2.0, however.

As with previous versions, a new .NET Compact Framework 3.5 was released in tandem with this update in order to provide support for additional features on Windows Mobile and Windows Embedded CE devices.

The source code of the Base Class Library in this version has been partially released (for debugging reference only) under the Microsoft Reference Source License

.NET Framework 3.0:

.NET Framework 3.0, formerly called WinFX, was released on 21 November 2006. It includes a new set of managed code APIs that are an integral part of Windows Vista and Windows Server 2008 operating systems. It is also available for Windows XP SP2 and Windows Server 2003 as a download. There are no major architectural changes included with this release; .NET Framework 3.0 uses the Common Language Runtime of .NET Framework 2.0. Unlike the previous major .NET releases there was no .NET Compact Framework release made as a counterpart of this version.

.NET Framework 3.0 consists of four major new components:

* Windows Presentation Foundation (WPF), formerly code-named Avalon; a new user interface subsystem and API based on XML and vector graphics, which uses 3D computer graphics hardware and Direct3D technologies. See WPF SDK for developer articles and documentation on WPF.
* Windows Communication Foundation (WCF), formerly code-named Indigo; a service-oriented messaging system which allows programs to interoperate locally or remotely similar to web services.
* Windows Workflow Foundation (WF) allows for building of task automation and integrated transactions using workflows.
* Windows CardSpace, formerly code-named InfoCard; a software component which securely stores a person's digital identities and provides a unified interface for choosing the identity for a particular transaction, such as logging in to a website.

.NET Framework 2.0

Released with Visual Studio 2005, Microsoft SQL Server 2005, and BizTalk 2006.

* The 2.0 Redistributable Package can be downloaded for free from Microsoft, and was published on 22 January 2006.
* The 2.0 Software Development Kit (SDK) can be downloaded for free from Microsoft.
* It is included as part of Visual Studio 2005 and Microsoft SQL Server 2005.
* Version 2.0 without any Service Pack is the last version with support for Windows 98 and Windows Me. Version 2.0 with Service Pack 2 is the last version with official support for Windows 2000 although there have been some unofficial workarounds published online to use a subset of the functionality from Version 3.5 in Windows 2000. Version 2.0 with Service Pack 2 requires Windows 2000 with SP4 plus KB835732 or KB891861 update, Windows XP with SP2 or later and Windows Installer 3.1 (KB893803-v2).
* It shipped with Windows Server 2003 R2 (not installed by default).

.NET Framework 1.1

This is the first major .NET Framework upgrade. It is available on its own as a redistributable package or in a software development kit, and was published on 3 April 2003. It is also part of the second release of Microsoft Visual Studio .NET (released as Visual Studio .NET 2003). This is the first version of the .NET Framework to be included as part of the Windows operating system, shipping with Windows Server 2003. Mainstream support for .NET Framework 1.1 ended on 14 October 2008, and extended support ends on 8 October 2013. Since .NET 1.1 is a component of Windows Server 2003, extended support for .NET 1.1 on Server 2003 will run out with that of the OS - currently 14 July 2015.

.NET Framework 1.0:
This is the first release of the .NET Framework, released on 13 February 2002 and available for Windows 98, Me, NT 4.0, 2000, and XP. Mainstream support by Microsoft for this version ended 10 July 2007, and extended support ended 14 July 2009.

DotNET Version

Changes in 1.1 on comparison with 1.0

* Built-in support for mobile ASP.NET controls. Previously available as an add-on for .NET Framework, now part of the framework.
* Security changes - enable Windows Forms assemblies to execute in a semi-trusted manner from the Internet, and enable Code Access Security in ASP.NET applications.
* Built-in support for ODBC and Oracle databases. Previously available as an add-on for .NET Framework 1.0, now part of the framework.
* .NET Compact Framework - a version of the .NET Framework for small devices.
* Internet Protocol version 6 (IPv6) support.
* Numerous API changes.

Changes in 2.0 in comparison with 1.1

* Numerous API changes.
* A new hosting API for native applications wishing to host an instance of the .NET runtime. The new API gives a fine grain control on the behavior of the runtime with regards to multithreading, memory allocation, assembly loading and more (detailed reference). It was initially developed to efficiently host the runtime in Microsoft SQL Server, which implements its own scheduler and memory manager.
* Full 64-bit support for both the x64 and the IA64 hardware platforms.
* Language support for generics built directly into the .NET CLR.
* Many additional and improved ASP.NET web controls.
* New data controls with declarative data binding.
* New personalization features for ASP.NET, such as support for themes, skins and webparts.
* .NET Micro Framework - a version of the .NET Framework related to the Smart Personal Objects Technology initiative.
* Partial classes
* Anonymous methods
* Data Tables

Changes since version 3.0

* New language features in C# 3.0 and VB.NET 9.0 compiler
* Adds support for expression trees and lambda methods
* Extension methods
* Expression trees to represent high-level source code at runtime.
* Anonymous types with static type inference
* Language Integrated Query (LINQ) along with its various providers
o LINQ to Objects
o LINQ to XML
o LINQ to SQL
* Paging support for ADO.NET
* ADO.NET synchronization API to synchronize local caches and server side datastores
* Asynchronous network I/O API.
* Peer-to-peer networking stack, including a managed PNRP resolver
* Managed wrappers for Windows Management Instrumentation and Active Directory APIs[25]
* Enhanced WCF and WF runtimes, which let WCF work with POX and JSON data, and also expose WF workflows as WCF services. WCF services can be made stateful using the WF persistence model.
* Support for HTTP pipelining and syndication feeds.
* ASP.NET AJAX is included
* New System.CodeDom namespace.

DOT NET Architecture

Common Language Infrastructure (CLI):
The purpose of the Common Language Infrastructure, or CLI, is to provide a language-neutral platform for application development and execution, including functions for exception handling, garbage collection, security, and interoperability. By implementing the core aspects of the .NET Framework within the scope of the CLI, this functionality will not be tied to a single language but will be available across the many languages supported by the framework. Microsoft's implementation of the CLI is called Common Language Runtime.

Assemblies:
The CIL code is housed in .NET assemblies. As mandated by specification, assemblies are stored in the Portable Executable (PE) format, common on the Windows platform for all DLL and EXE files. The assembly consists of one or more files, one of which must contain the manifest, which has the metadata for the assembly. The complete name of an assembly (not to be confused with the filename on disk) contains its simple text name, version number, culture, and public key token. The public key token is a unique hash generated when the assembly is compiled, thus two assemblies with the same public key token are guaranteed to be identical from the point of view of the framework. A private key can also be specified known only to the creator of the assembly and can be used for strong naming and to guarantee that the assembly is from the same author when a new version of the assembly is compiled (required to add an assembly to the Global Assembly Cache).

Metadata:
All CIL is self-describing through .NET metadata. The CLR checks the metadata to ensure that the correct method is called. Metadata is usually generated by language compilers but developers can create their own metadata through custom attributes. Metadata contains information about the assembly, and is also used to implement the reflective programming capabilities of .NET Framework.

Security:
.NET has its own security mechanism with two general features: Code Access Security (CAS), and validation and verification. Code Access Security is based on evidence that is associated with a specific assembly. Typically the evidence is the source of the assembly (whether it is installed on the local machine or has been downloaded from the intranet or Internet). Code Access Security uses evidence to determine the permissions granted to the code. Other code can demand that calling code is granted a specified permission. The demand causes the CLR to perform a call stack walk: every assembly of each method in the call stack is checked for the required permission; if any assembly is not granted the permission a security exception is thrown.

When an assembly is loaded the CLR performs various tests. Two such tests are validation and verification. During validation the CLR checks that the assembly contains valid metadata and CIL, and whether the internal tables are correct. Verification is not so exact. The verification mechanism checks to see if the code does anything that is 'unsafe'. The algorithm used is quite conservative; hence occasionally code that is 'safe' does not pass. Unsafe code will only be executed if the assembly has the 'skip verification' permission, which generally means code that is installed on the local machine.

.NET Framework uses appdomains as a mechanism for isolating code running in a process. Appdomains can be created and code loaded into or unloaded from them independent of other appdomains. This helps increase the fault tolerance of the application, as faults or crashes in one appdomain do not affect rest of the application. Appdomains can also be configured independently with different security privileges. This can help increase the security of the application by isolating potentially unsafe code. The developer, however, has to split the application into subdomains; it is not done by the CLR.

Class library:
The .NET Framework includes a set of standard class libraries. The class library is organized in a hierarchy of namespaces. Most of the built in APIs are part of either System.* or Microsoft.* namespaces. These class libraries implement a large number of common functions, such as file reading and writing, graphic rendering, database interaction, and XML document manipulation, among others. The .NET class libraries are available to all .NET languages. The .NET Framework class library is divided into two parts: the Base Class Library and the Framework Class Library.

The Base Class Library (BCL) includes a small subset of the entire class library and is the core set of classes that serve as the basic API of the Common Language Runtime.[10] The classes in mscorlib.dll and some of the classes in System.dll and System.core.dll are considered to be a part of the BCL. The BCL classes are available in both .NET Framework as well as its alternative implementations including .NET Compact Framework, Microsoft Silverlight and Mono.

The Framework Class Library (FCL) is a superset of the BCL classes and refers to the entire class library that ships with .NET Framework. It includes an expanded set of libraries, including WinForms, ADO.NET, ASP.NET, Language Integrated Query, Windows Presentation Foundation, Windows Communication Foundation among others. The FCL is much larger in scope than standard libraries for languages like C++, and comparable in scope to the standard libraries of Java.

Memory management:
The .NET Framework CLR frees the developer from the burden of managing memory (allocating and freeing up when done); instead it does the memory management itself. To this end, the memory allocated to instantiations of .NET types (objects) is done contiguously from the managed heap, a pool of memory managed by the CLR. As long as there exists a reference to an object, which might be either a direct reference to an object or via a graph of objects, the object is considered to be in use by the CLR. When there is no reference to an object, and it cannot be reached or used, it becomes garbage. However, it still holds on to the memory allocated to it. .NET Framework includes a garbage collector which runs periodically, on a separate thread from the application's thread, that enumerates all the unusable objects and reclaims the memory allocated to them.

The .NET Garbage Collector (GC) is a non-deterministic, compacting, mark-and-sweep garbage collector. The GC runs only when a certain amount of memory has been used or there is enough pressure for memory on the system. Since it is not guaranteed when the conditions to reclaim memory are reached, the GC runs are non-deterministic. Each .NET application has a set of roots, which are pointers to objects on the managed heap (managed objects). These include references to static objects and objects defined as local variables or method parameters currently in scope, as well as objects referred to by CPU registers. When the GC runs, it pauses the application, and for each object referred to in the root, it recursively enumerates all the objects reachable from the root objects and marks them as reachable. It uses .NET metadata and reflection to discover the objects encapsulated by an object, and then recursively walk them. It then enumerates all the objects on the heap (which were initially allocated contiguously) using reflection. All objects not marked as reachable are garbage. This is the mark phase. Since the memory held by garbage is not of any consequence, it is considered free space. However, this leaves chunks of free space between objects which were initially contiguous. The objects are then compacted together, by using memcpy to copy them over to the free space to make them contiguous again. Any reference to an object invalidated by moving the object is updated to reflect the new location by the GC. The application is resumed after the garbage collection is over.

The GC used by .NET Framework is actually generational. Objects are assigned a generation; newly created objects belong to Generation 0. The objects that survive a garbage collection are tagged as Generation 1, and the Generation 1 objects that survive another collection are Generation 2 objects. The .NET Framework uses up to Generation 2 objects. Higher generation objects are garbage collected less frequently than lower generation objects. This helps increase the efficiency of garbage collection, as older objects tend to have a larger lifetime than newer objects. Thus, by removing older (and thus more likely to survive a collection) objects from the scope of a collection run, fewer objects need to be checked and compacted.

DOT NET Principal design features

Interoperability
Because interaction between new and older applications is commonly required, the .NET Framework provides means to access functionality that is implemented in programs that execute outside the .NET environment. Access to COM components is provided in the System.Runtime.InteropServices and System.EnterpriseServices namespaces of the framework; access to other functionality is provided using the P/Invoke feature.
Common Runtime Engine
The Common Language Runtime (CLR) is the virtual machine component of the .NET framework. All .NET programs execute under the supervision of the CLR, guaranteeing certain properties and behaviors in the areas of memory management, security, and exception handling.
Language Independence
The .NET Framework introduces a Common Type System , or CTS. The CTS defines all possible datatypes and programming constructs supported by the CLR and how they may or may not interact with each other. Because of this feature, the .NET Framework supports the exchange of instances of types between programs written in any of the .NET languages. This is discussed in more detail in Microsoft .NET Languages.
Base Class Library
The Base Class Library (BCL), part of the Framework Class Library (FCL), is a library of functionality available to all languages using the .NET Framework. The BCL provides classes which encapsulate a number of common functions, including file reading and writing, graphic rendering , interaction and XML document manipulation.
Simplified Deployment
The .NET framework includes design features and tools that help manage the installation of computer software to ensure that it does not interfere with previously installed software, and that it conforms to security requirements.
Security
The design is meant to address some of the vulnerabilities, such as buffer overflows , that have been exploited by malicious software. Additionally, .NET provides a common security model for all applications.
Portability
The design of the .NET Framework allows it to theoretically be platform agnostic, and thus cross-platform compatible. That is, a program written to use the framework should run without change on any type of system for which the framework is implemented. Microsoft's commercial implementations of the framework cover Windows, Windows CE , and the Xbox 360 . In addition, Microsoft submits the specifications for the Common Language Infrastructure (which includes the core class libraries, Common Type System , and the Common Intermediate Language ) making them available as open standards. This makes it possible for third parties to create compatible implementations of the framework and its languages on other platforms.