Interview Questions

Basic .NET and ASP.NET interview questionsExplain the .NET architecture. How many languages .NET is supporting now? - When .NET was introduced it came with several languages. VB.NET, C#, COBOL and Perl, etc. The site DotNetLanguages.Net says 44 languages are supported. (Check in Page -12)
How is .NET able to support multiple languages? - a language should comply with the Common Language Runtime standard to become a .NET language. In .NET, code is compiled to Microsoft Intermediate Language (MSIL for short). This is called as Managed Code. This Managed code is run in .NET environment. So after compilation to this IL the language is not a barrier. A code can call or use a function written in another language.
How ASP .NET different from ASP? - Scripting is separated from the HTML, Code is compiled as a DLL, these DLLs can be executed on the server.
Resource Files: How to use the resource files, how to know which language to use?What is smart navigation? - The cursor position is maintained when the page gets refreshed due to the server side validation and the page gets refreshed.
What is view state? - The web is stateless. But in ASP.NET, the state of a page is maintained in the in the page itself automatically. How? The values are encrypted and saved in hidden controls. this is done automatically by the ASP.NET. This can be switched off / on for a single controlExplain the life cycle of an ASP .NET page.
How do you validate the controls in an ASP .NET page? - Using special validation controls that are meant for this. We have Range Validator, Email Validator.Can the validation be done in the server side? Or this can be done only in the Client side? - Client side is done by default. Server side validation is also possible. We can switch off the client side and server side can be done.
How to manage pagination in a page? - Using pagination option in DataGrid control. We have to set the number of records for a page, then it takes care of pagination by itself.What is ADO .NET and what is difference between ADO and ADO.NET? - ADO.NET is stateless mechanism. I can treat the ADO.Net as a separate in-memory database where in I can use relationships between the tables and select insert and updates to the database. I can update the actual database as a batch.
Interview Questions - C#What’s the implicit name of the parameter that gets passed into the class’ set method?Value, and its datatype depends on whatever variable we’re changing.How do you inherit from a class in C#? Place a colon and then the name of the base class. Notice that it’s double colon in C++.
Does C# support multiple inheritance? No, use interfaces instead.When you inherit a protected class-level variable, who is it available to? Classes in the same namespace.
Are private class-level variables inherited? Yes, but they are not accessible, so looking at it you can honestly say that they are not inherited. But they are.Describe the accessibility modifier protected internal. It’s available to derived classes and classes within the same Assembly (and naturally from the base class it’s declared in).C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one.
How many constructors should I write? Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there’s no implementation in it.
What’s the top .NET class that everything is derived from? System.Object.
How’s method overriding different from overloading? When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.What does the keyword virtual mean in the method definition? The method can be over-ridden.Can you declare the override method static while the original method is non-static? No, you can’t, the signature of the virtual method must remain the same, only the keyword virtual is changed to keyword override.
Can you override private virtual methods? No, moreover, you cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.Can you prevent your class from being inherited and becoming a base class for some other classes? Yes, that’s what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It’s the same concept as final class in Java.
Can you allow class to be inherited, but prevent the method from being over-ridden? Yes, just leave the class public and make the method sealed.What’s an abstract class? A class that cannot be instantiated. A concept in C++ known as pure virtual method. A class that must be inherited and have the methods over-ridden. Essentially, it’s a blueprint for a class without any implementation.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)? When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.What’s an interface class? It’s an abstract class with public abstract methods all of which must be implemented in the inherited classes.
Why can’t you specify the accessibility modifier for methods inside the interface? They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it’s public by default.Can you inherit multiple interfaces? Yes, why not.And if they have conflicting method names? It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay.
What’s the difference between an interface and abstract class? In the interface all methods must be abstract; in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.
How can you overload a method? Different parameter data types, different number of parameters, different order of parameters.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor? Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
What’s the difference between System.String and System.StringBuilder classes? System.String is immutable; System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
What’s the advantage of using System.Text.StringBuilder over System.String? StringBuilder is more efficient in the cases, where a lot of manipulation is done to the text. Strings are immutable, so each time it’s being operated on, a new instance is created.
Can you store multiple data types in System.Array? No.
What’s the difference between the System.Array.CopyTo() and System.Array.Clone()? The first one performs a deep copy of the array, the second one is shallow.
How can you sort the elements of the array in descending order? By calling Sort() and then Reverse() methods.What’s the .NET datatype that allows the retrieval of data by a unique key? HashTable.
What’s class SortedList underneath? A sorted HashTable.
Will finally block get executed if the exception had not occurred? Yes.
What’s the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
Can multiple catch blocks be executed? No, once the proper catch code fires off, the control is transferred to the finally block (if there are any), and then whatever follows the finally block.
Why is it a bad idea to throw your own exceptions? Well, if at that point you know that an error has occurred, then why not write the proper code to handle that error instead of passing a new Exception object to the catch block? Throwing your own exceptions signifies some design flaws in the project.
What’s a delegate? A delegate object encapsulates a reference to a method. In C++ they were referred to as function pointers.
What’s a multicast delegate? It’s a delegate that points to and eventually fires off several methods.How’s the DLL Hell problem solved in .NET? Assembly versioning allows the application to specify not only the library it needs to run (which was available under Win32), but also the version of the assembly.
What are the ways to deploy an assembly? An MSI installer, a CAB archive, and XCOPY command.
What’s a satellite assembly? When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
What namespaces are necessary to create a localized application? System.Globalization, System.Resources.What’s the difference between // comments, /* */ comments and /// comments? Single-line, multi-line and XML documentation comments.How do you generate documentation from the C# file commented properly with a command-line compiler? Compile it with a /doc switch.
What’s the difference between and XML documentation tag? Single line code example and multiple-line code example.Is XML case-sensitive? Yes, so and are different elements.What debugging tools come with the .NET SDK? CorDBG – command-line debugger, and DbgCLR – graphic debugger. Visual Studio .NET uses the DbgCLR. To use CorDbg, you must compile the original C# file using the /debug switch.
What does the This window show in the debugger? It points to the object that’s pointed to by this reference. Object’s instance data is shown.
What does assert() do? In debug compilation, assert takes in a Boolean condition as a parameter, and shows the error dialog if the condition is false. The program proceeds without any interruption if the condition is true.
What’s the difference between the Debug class and Trace class? Documentation looks the same. Use Debug class for debug builds, use Trace class for both debug and release builds.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher? The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.Where is the output of TextWriterTraceListener redirected? To the Console or a text file depending on the parameter passed to the constructor.
How do you debug an ASP.NET Web application? Attach the aspnet_wp.exe process to the DbgClr debugger.
What are three test cases you should go through in unit testing? Positive test cases (correct data, correct output), negative test cases (broken or missing data, proper handling), exception test cases (exceptions are thrown and caught properly).
Can you change the value of a variable while debugging a C# application? Yes, if you are debugging via Visual Studio.NET, just go to Immediate window.
Explain the three services model (three-tier application). Presentation (UI), business (logic and underlying code) and data (from storage or other sources).
What are advantages and disadvantages of Microsoft-provided data provider classes in ADO.NET? SQLServer.NET data provider is high-speed and robust, but requires SQL Server license purchased from Microsoft. OLE-DB.NET is universal for accessing other sources, like Oracle, DB2, Microsoft Access and Informix, but it’s a .NET layer on top of OLE layer, so not the fastest thing in the world. ODBC.NET is a deprecated layer provided for backward compatibility to ODBC engines.
What’s the role of the DataReader class in ADO.NET connections? It returns a read-only dataset from the data source when the command is executed.
What is the wildcard character in SQL? Let’s say you want to query database with LIKE for all employees whose name starts with La. The wildcard character is %, the proper query with LIKE would involve ‘La%’.
Explain ACID rule of thumb for transactions. Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no “in-between” case where something has been updated and something hasn’t), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
What connections does Microsoft SQL Server support? Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords).
Which one is trusted and which one is untrusted? Windows Authentication is trusted because the username and password are checked with the Active Directory, the SQL Server authentication is untrusted, since SQL Server is the only verifier participating in the transaction.
Why would you use untrusted verificaion? Web Services might use it, as well as non-Windows applications.What does the parameter Initial Catalog define inside Connection String? The database name to connect to.
What’s the data provider name to connect to Access database? Microsoft.Access.
What does Dispose method do with the connection object? Deletes it from the memory.What is a pre-requisite for connection pooling? Multiple processes must agree that they will share the same connection, where every parameter is the same, including the security settings.
General Questions1. Does C# support multiple-inheritance? No.
2. Who is a protected class-level variable available to? It is available to any sub-class (a class inheriting this class).
3. Are private class-level variables inherited? Yes, but they are not accessible. Although they are not visible or accessible via the class interface, they are inherited.
4. Describe the accessibility modifier “protected internal”. It is available to classes that are within the same assembly and derived from the specified base class.
5. What’s the top .NET class that everything is derived from? System.Object.
6. What does the term immutable mean?The data value may not be changed. Note: The variable value may be changed, but the original immutable data value was discarded and a new data value was created in memory.
7. What’s the difference between System.String and System.Text.StringBuilder classes?
System.String is immutable. System.StringBuilder was designed with the purpose of having a mutable string where a variety of operations can be performed.
8. What’s the advantage of using System.Text.StringBuilder over System.String?StringBuilder is more efficient in cases where there is a large amount of string manipulation. Strings are immutable, so each time a string is changed, a new instance in memory is created.9. Can you store multiple data types in System.Array?No.
10. What’s the difference between the System.Array.CopyTo() and System.Array.Clone()?
The Clone() method returns a new array (a shallow copy) object containing all the elements in the original array. The CopyTo() method copies the elements into another existing array. Both perform a shallow copy. A shallow copy means the contents (each array element) contains references to the same object as the elements in the original array. A deep copy (which neither of these methods performs) would create a new instance of each element's object, resulting in a different, yet identacle object.
11. How can you sort the elements of the array in descending order?By calling Sort() and then Reverse() methods.
12. What’s the .NET collection class that allows an element to be accessed using a unique key?HashTable.
13. What class is underneath the SortedList class?A sorted HashTable.
14. Will the finally block get executed if an exception has not occurred?­Yes.15. What’s the C# syntax to catch any possible exception?A catch block that catches the exception of type System.Exception. You can also omit the parameter data type in this case and just write catch {}.
16. Can multiple catch blocks be executed for a single try statement?No. Once the proper catch block processed, control is transferred to the finally block (if there are any).
17. Explain the three services model commonly know as a three-tier application.Presentation (UI), Business (logic and underlying code) and Data (from storage or other sources).
Class Questions1. What is the syntax to inherit from a class in C#? Place a colon and then the name of the base class.Example: class MyNewClass : MyBaseClass
2. Can you prevent your class from being inherited by another class? Yes. The keyword “sealed” will prevent the class from being inherited.
3. Can you allow a class to be inherited, but prevent the method from being over-ridden?Yes. Just leave the class public and make the method sealed.
4. What’s an abstract class?A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
5. When do you absolutely have to declare a class as abstract?1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden. 2. When at least one of the methods in the class is abstract.
6. What is an interface class?Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide implementation. They are implemented by classes, and defined as separate entities from classes.
7. Why can’t you specify the accessibility modifier for methods inside the interface?They all must be public, and are therefore public by default.
8. Can you inherit multiple interfaces?Yes. .NET does support multiple interfaces.
9. What happens if you inherit multiple interfaces and they have conflicting method names?It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay. To Do: Investigate
10. What’s the difference between an interface and abstract class?In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers.
11. What is the difference between a Struct and a Class?Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.
Method and Property Questions1. What’s the implicit name of the parameter that gets passed into the set method/property of a class? Value. The data type of the value parameter is defined by whatever data type the property is declared as.
2. What does the keyword “virtual” declare for a method or property? The method or property can be overridden.
3. How is method overriding different from method overloading? When overriding a method, you change the behavior of the method for the derived class. Overloading a method simply involves having another method with the same name within the class.
4. Can you declare an override method to be static if the original method is not static? No. The signature of the virtual method must remain the same. (Note: Only the keyword virtual is changed to keyword override)
5. What are the different ways a method can be overloaded? Different parameter data types, different number of parameters, different order of parameters.
6. If a base class has a number of overloaded constructors, and an inheriting class has a number of overloaded constructors; can you enforce a call from an inherited constructor to a specific base constructor?Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.

1. How to enable the mnemonics (underline) being displayed when an application is launched?Usually the underline appears only after you press the Alt Key, but you can enable it by changing the Operating System Settings. On Windows XP, Right Click Desktop to bring up the Display Properties Dialog and then choose Appearance tab and then the Effects Button and uncheck the checkbox "Hide Underlined letters for keyboard navigation until I press the ALT Key".----------------------------------------------------------------------------------------------------------------------------------2. An easy way to build connection string.Though this in not related to .NET directly but it is useful while working with ADO.NETCollapse1) Open a New notepad and save it with "udl" extension, suppose "New.udl".2) Now you will see that it's icon is changed.3) Open it, you will find Data Link properties dialog box.4) For SQl Server connection string select Microsoft OLE DB Provider For SQL Server in Provider Tab.5) Click button "Next" or select Connection Tab6) Here you can select all connection details and press button Test Connection. If it is successful close this dialog box.7) Now open this file using "Notepad", you will find the connection string. Though it is built for OLE DB type of connection, you can use for SQL Server connection by removing Provider attribute. NOTE: If you are using SQL Authentication with password, then check the checkbox Allow Saving Password.This is necessary so that password appears in connection string.----------------------------------------------------------------------------------------------------------------------------------3. How to add a custom or destination folder to SendTo menu?Every one knows about SendTo menu that appears after right click on any file.By default there are 4 options or destinations in this menu. But you can add custom destinations to this menu. Adding other locations to the Send To menu is convenient if you frequently perform the same file management tasks. For example, if you back up files on another network computer or on same machine where you have to navigate through a deep path every day, having the computer on the Send To menu can save you time.To add a destination to the Send To menu follow the steps given below:Open My Computer.Double-click the drive where Windows is installed (usually drive C, unless you have more than one drive on your computer). If you can't see the items on your drive when you open it, under System Tasks, click Show the contents of this drive.Double-click the Documents and Settings folder.Double-click the folder of a specific user.Double-click the SendTo folder. The SendTo folder is hidden by default. If it is not visible, on the Tools menu, click Folder Options. On the View tab, click Show hidden files and folders.On the File menu, point to New, and then click Shortcut.Follow the instructions on your screen.----------------------------------------------------------------------------------------------------------------------------------4)Read a text fileThe following sample code uses a StreamReader class to read the System.ini file. The contents of the file are added to a ListBox control. The try...catch block is used to alert the program if the file is empty. There are many ways to determine when the end of the file is reached; this sample uses the Peek method to examine the next line before reading it.Dim reader As StreamReader = _ New StreamReader(winDir & "\system.ini") Try Me.ListBox1.Items.Clear() Do Me.ListBox1.Items.Add(reader.ReadLine) Loop Until reader.Peek = -1 Catch Me.ListBox1.Items.Add("File is empty") Finally reader.Close() End Try----------------------------------------------------------------------------------------------------------------------------------5)Write a text fileThis sample code uses a StreamWriter class to create and write to a file. If you have an existing file, you can open it in the same way.Dim writer As StreamWriter = _ New StreamWriter("c:\KBTest.txt") writer.WriteLine("File created using StreamWriter class.") writer.Close()----------------------------------------------------------------------------------------------------------------------------------6) View file informationThis sample code uses a FileInfo object to access a file's properties. Notepad.exe is used in this example. The properties appear in a ListBox control.Dim FileProps As FileInfo = New FileInfo(winDir & "\notepad.exe") With Me.ListBox1.Items .Clear() .Add("File Name = " & FileProps.FullName) .Add("Creation Time = " & FileProps.CreationTime) .Add("Last Access Time = " & FileProps.LastAccessTime) .Add("Last Write Time = " & FileProps.LastWriteTime) .Add("Size = " & FileProps.Length) End With FileProps = Nothing----------------------------------------------------------------------------------------------------------------------------------7) List disk drivesThis sample code uses the Directory and Drive classes to list the logical drives on a system. For this sample, the results appear in a ListBox control.Dim dirInfo As Directory Dim drive As String Me.ListBox1.Items.Clear() Dim drives() As String = dirInfo.GetLogicalDrives() For Each drive In drives Me.ListBox1.Items.Add(drive) Next----------------------------------------------------------------------------------------------------------------------------------8)List subfoldersThis sample code uses the GetDirectories method of the Directory class to get a list of folders.Dim dir As String Me.ListBox1.Items.Clear() Dim dirs() As String = Directory.GetDirectories(winDir) For Each dir In dirs Me.ListBox1.Items.Add(dir) Next----------------------------------------------------------------------------------------------------------------------------------9)List filesThis sample code uses the GetFiles method of the Directory class to get a list of files.Dim file As String Me.ListBox1.Items.Clear() Dim files() As String = Directory.GetFiles(winDir) For Each file In files Me.ListBox1.Items.Add(file) Next----------------------------------------------------------------------------------------------------------------------------------SQL Server10) Using add linked server for connecting one server to another external Database serverConnecting Another DB with windows authenticationexec sp_addlinkedserver [intranetbd]Connecting Another DB with User defined authentication Syntax:EXEC sp_addlinkedsrvlogin 'Accounts', 'false', NULL, 'SQLUser', 'Password'Ex: exec sp_addlinkedsrvlogin [intranetbd],false,'qteam','tsms','Hr'Accessing the DB serverselect DISTINCT c_id from [intranetbd].Hr.dbo.projectsFound under SQL Server 2005Server objects -> Linked server----------------------------------------------------------------------------------------------------------------------------------11. Sub Query – Query within QueryEx : select * from EMP Where Id not in (SELECT Max(Id) from EMP group by Name) order by name----------------------------------------------------------------------------------------------------------------------------------12. Write query to get 10 records (random wise) from Table, with out use DESC and TOP Command.Query : select (select count(*) from Empwhere Name <= t.Name) as SRNo,* from Emp t where 11<=(select count(*) from Emp where Name <= t.Name)and 20>=(select count(*) from Emp where Name <= t.Name)order by Name----------------------------------------------------------------------------------------------------------------------------------13. Write query to using Having Statement: ->It can be used with group by and aggregate function like avg, sum, max, min, etc,. Exampleselect count(Name) from Emp group by Name having count(Name)>1----------------------------------------------------------------------------------------------------------------------------------14) using Substring and charindexCHARINDEX SYNTAX CHARINDEX( text to find, text ) => 11 Example CHARINDEX('SQL', 'Microsoft SQL Server') => 11 SUBSTRING SYNTAXSUBSTRING ( expression , start , length )ExampleSELECT x = SUBSTRING('abcdef', 2, 3) => bcdCombined Example – 1 :SELECT SUBSTRING(email, 1, CHARINDEX('@', email) - 1) AS EmailFROM Active_employee_listCombined Example – 2 :select left(mail_id,charindex('@',mail_id)-1) from emp_personalResult : jayavelcs@gmail.com -> jayavelcs----------------------------------------------------------------------------------------------------------------------------------15) using Stored ProcedureA stored procedure is a named group of SQL statements that have been previously created and stored in the server database. Stored procedures accept input parameters so that a single procedure can be used over the network by several clients using different input data. Stored procedures reduce network traffic and improve performance.Ex 1:CREATE PROCEDURE sp_myStoredProcedureASSelect column1, column2 From Table1Ex2:CREATE PROCEDURE sp_myStoredProcedure @myInput intASSelect column1, column2 From Table1Where column1 = @myInputEx3:CREATE PROCEDURE sp_myStoredProcedure @myInput int, @myString varchar(100), @myFloatAS Ex4:CREATE PROCEDURE sp_myInsert @FirstName varchar(20), @LastName varchar(30)AsINSERT INTO Names(FirstName, LastName)values(@FirstName, @LastName)Alter Procedurealter procedure Drop procedureDrop procedure ExecutingExec sp_myStoredProcedure 0, 'This is my string', 3.45----------------------------------------------------------------------------------------------------------------------------------16) Conversion format : Here is the output from the above script:Type 1:select * from audit_table where convert(datetime,left(actual_audit_date,11))='09/06/2007'Type 2:1) CONVERT(CHAR(19),GETDATE()) ==>Feb 5 2003 5:54AM2) CONVERT(CHAR(8),GETDATE(),10 ) ==>02-05-033) CONVERT(CHAR(10),GETDATE(),110) ==>02-05-20034) CONVERT(CHAR(11),GETDATE(),106) ==>05 Feb 20035) CONVERT(CHAR(9),GETDATE(),6) ==>05 Feb 036) CONVERT(CHAR(24),GETDATE(),113) ==>05 Feb 2003 05:54:39:56----------------------------------------------------------------------------------------------------------------------------------17) Using Temp tableCreatingcreate table #tableTmp (empid varchar(50))Insertinginsert into #tableTmpselect emp_id from Bats_Log_Emp_Revenue where txn_name = 'Add Partner Employee'Using select @NoTrans = count(distinct empid) from #tableTmpDeletingdrop table #tableTmp----------------------------------------------------------------------------------------------------------------------------------18) Importing data from Excel to SQL ServerSelect Database --> Right mouse click -- > Import data.The wizard starts and it self-driven.Through programmatically SELECT * INTO db1.dbo.table1FROM OPENROWSET('MSDASQL', 'Driver={Microsoft Excel Driver (*.xls)};DBQ=c:\book1.xls', 'SELECT * FROM [sheet1$]')----------------------------------------------------------------------------------------------------------------------------------19) Executing exe from SQL Serverdeclare @cmd varchar(8000)set @cmd = 'cmd.exe /C "D:\Scheduled Tasks\LinuxBackup.exe "'EXEC xp_cmdshell @cmd----------------------------------------------------------------------------------------------------------------------------------20) Shrink Database Log File SizeUSE wss_content;GO-- Truncate the log by changing the database recovery model to SIMPLE.ALTER DATABASE wss_contentSET RECOVERY SIMPLE;GO-- Shrink the truncated log file to 100 MB.DBCC SHRINKFILE (wss_content_Log, 100);GO-- Reset the database recovery model.ALTER DATABASE wss_contentSET RECOVERY FULL;GO----------------------------------------------------------------------------------------------------------------------------------21) String FunctionsLEFT(S , N):Returns the first N characters of string S from the left.Example: LEFT('Function',6)='Functi'RIGHT(S , N) : Returns the last N characters of string S from the right.Example: RIGHT('Function',6)='nction'LEN (S): Returns the number of characters in string S.Example: LEN ('Function',6)=8LOWER (S): Return string S after converting all characters to lower case.Example: LOWER ('Function')='function'UPPER (S): Return string S after converting all characters to upper case.Example: UPPER ('Function')='FUNCTION'LTRIM (S): Return string S after removing all blank characters from the left.Example: LTRIM (' Function')='Function'RTRIM (S): Return string S after removing all blank characters from the right.Example: RTRIM ('Function ')='Function'REPLACE ( S1 ,S2 ,S3 ): Return S1 after replacing all occurrence of S2 in it with S3Example: REPLACE ('Function','n','123')='Fu123ctio123'REPLICATE ( S , N): Return a repetition of string S, N timesExample: REPLICATE ('abc',3)='abcabcabc'REVERSE ( S) : Return string S after reversing the order of all characters.Example: REVERSE ('Function')=' noitcnuF'SPACE(N): Return a string of repeated spaces N times.Example: SPACE(4)=' 'STUFF ( S , I, N, S1): Return string S after deleting N characters from index I and inserting S1 at position I.Example: STUFF ('Function', 3, 4,'abc' )='Fuabcon'SUBSTRING ( S, I, N): Return a portion of S from index I of N characters.Example: SUBSTRING ('Function', 3, 4)='ncti'------------------------------------------------------------------------------------------------------------------------------------------1) Aggregate FunctionsAVG ( [ ALL DISTINCT ] E ) : Return the average of not null values of expression E. If ALL parameter is specify the function is apply to all values, it is the default value. If DISTINCT parameter is specify the function is apply only on each occurrence of the value.Example: SELECT HOURS FROM Employee returns (7, 8, 10, 5, 4, 6, 8, 7, 11, 10, 12) SELECT AVG(HOURS) FROM Employee returns (8) SELECT AVG(DISTINCT HOURS) FROM Employee returns (7)COUNT ( [ ALL DISTINCT ] E ]) : Return the number of item in the group of expression E. If E=* the function will return the number of record in the data source. If ALL parameter is specify the function is apply to all values, it is the default value. If DISTINCT parameter is specify the function is apply only on each occurrence of the value. The parameter ALL and DISTINCT can not be use with *.MAX(E): Return the maximum value of expression E.Example: SELECT HOURS FROM Employee returns (7, 8, 10, 5, 4, 6, 8, 7, 11, 10, 12) SELECT MAX(HOURS) FROM Employee return (12)MIN(E): Return the minimum value of expression E.Example: SELECT HOURS FROM Employee returns (7, 8, 10, 5, 4, 6, 8, 7, 11, 10, 12)SELECT MIN(HOURS) FROM Employee return (4)SUM ( [ ALL DISTINCT ] E): Return the SUM of not null values of expression E. If ALL parameter is specify the function is apply to all values, it is the default value. If DISTINCT parameter is specify the function is apply only on each occurrence of the value. SUM can be use numeric columns only.Example: SELECT HOURS FROM Employee returns (7, 8, 10, 5, 4, 6, 8, 7, 11, 10, 12) SELECT SUM(HOURS) FROM Employee returns (88) SELECT SUM(DISTINCT HOURS) FROM Employee returns (63)------------------------------------------------------------------------------------------------------------------------------------------29) Using Data type ConversationsExplicitly converts an expression of one data type to another. CAST and CONVERT provide similar functionality.SyntaxCAST ( expression AS data_type )CONVERT ( data_type [ ( length ) ] , expression [ , style ] )Ex:CONVERT(decimal(10,5), @myval)------------------------------------------------------------------------------------------------------------------------------------------27) Try –Catch BEGIN TRYEXEC dbo.sp_bcr_import_data_reportEND TRYBEGIN CATCHPRINT 'Test';RETURN;END CATCH------------------------------------------------------------------------------------------------------------------------------------------28) Begin Tran – End Tran gobegin tran mytrans;insert into table1 values (1, 'test');insert into table1 values (1, 'jsaureouwrolsjflseorwurw'); -- it will encounter error here since max value to be inputted is 10commit tran mytrans;

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What are the basic functions of an operating system? - Operating system controls and coordinates the use of the hardware among the various applications programs for various uses. Operating system acts as resource allocator and manager. Since there are many possibly conflicting requests for resources the operating system must decide which requests are allocated resources to operating the computer system efficiently and fairly. Also operating system is control program which controls the user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.

Why paging is used? - Paging is solution to external fragmentation problem which is to permit the logical address space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.
While running DOS on a PC, which command would be used to duplicate the entire diskette? diskcopy

What resources are used when a thread created? How do they differ from those when a process is created? - When a thread is created the threads does not require any new resources to execute the thread shares the resources like memory of the process to which they belong to. The benefit of code sharing is that it allows an application to have several different threads of activity all within the same address space. Whereas if a new process creation is very heavyweight because it always requires new address space to be created and even if they share the memory then the inter process communication is expensive when compared to the communication between the threads.

What is virtual memory? - Virtual memory is hardware technique where the system appears to have more memory that it actually does. This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used.
What is Throughput, Turnaround time, waiting time and Response time? - Throughput – number of processes that complete their execution per time unit. Turnaround time – amount of time to execute a particular process. Waiting time – amount of time a process has been waiting in the ready queue. Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment).
What is the state of the processor, when a process is waiting for some event to occur? - Waiting state

What is the important aspect of a real-time system or Mission Critical Systems? - A real time operating system has well defined fixed time constraints. Process must be done within the defined constraints or the system will fail. An example is the operating system for a flight control computer or an advanced jet airplane. Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems. Real-Time systems may be either hard or soft real-time. Hard real-time: Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM), Conflicts with time-sharing systems, not supported by general-purpose operating systems. Soft real-time: Limited utility in industrial control of robotics, Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.
What is the difference between Hard and Soft real-time systems? - A hard real-time system guarantees that critical tasks complete on time. This goal requires that all delays in the system be bounded from the retrieval of the stored data to the time that it takes the operating system to finish any request made of it. A soft real time system where a critical real-time task gets priority over other tasks and retains that priority until it completes. As in hard real time systems kernel delays need to be bounded

What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? - Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.

What is multi tasking, multi programming, multi threading? - Multi programming: Multiprogramming is the technique of running several programs at a time using timesharing. It allows a computer to do several things at the same time. Multiprogramming creates logical parallelism. The concept of multiprogramming is that the operating system keeps several jobs in memory simultaneously. The operating system selects a job from the job pool and starts executing a job, when that job needs to wait for any i/o operations the CPU is switched to another job. So the main idea here is that the CPU is never idle. Multi tasking: Multitasking is the logical extension of multiprogramming .The concept of multitasking is quite similar to multiprogramming but difference is that the switching between jobs occurs so frequently that the users can interact with each program while it is running. This concept is also known as time-sharing systems. A time-shared operating system uses CPU scheduling and multiprogramming to provide each user with a small portion of time-shared system. Multi threading: An application typically is implemented as a separate process with several threads of control. In some situations a single application may be required to perform several similar tasks for example a web server accepts client requests for web pages, images, sound, and so forth. A busy web server may have several of clients concurrently accessing it. If the web server ran as a traditional single-threaded process, it would be able to service only one client at a time. The amount of time that a client might have to wait for its request to be serviced could be enormous. So it is efficient to have one process that contains multiple threads to serve the same purpose. This approach would multithread the web-server process, the server would create a separate thread that would listen for client requests when a request was made rather than creating another process it would create another thread to service the request. To get the advantages like responsiveness, Resource sharing economy and utilization of multiprocessor architectures multithreading concept can be used.

What is hard disk and what is its purpose? - Hard disk is the secondary storage device, which holds the data in bulk, and it holds the data on the magnetic medium of the disk.Hard disks have a hard platter that holds the magnetic medium, the magnetic medium can be easily erased and rewritten, and a typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files.

What is fragmentation? Different types of fragmentation? - Fragmentation occurs in a dynamic memory allocation system when many of the free blocks are too small to satisfy any request. External Fragmentation: External Fragmentation happens when a dynamic memory allocation algorithm allocates some memory and a small piece is left over that cannot be effectively used. If too much external fragmentation occurs, the amount of usable memory is drastically reduced. Total memory space exists to satisfy a request, but it is not contiguous. Internal Fragmentation: Internal fragmentation is the space wasted inside of allocated memory blocks because of restriction on the allowed sizes of allocated blocks. Allocated memory may be slightly larger than requested memory; this size difference is memory internal to a partition, but not being used

What is DRAM? In which form does it store data? - DRAM is not the best, but it’s cheap, does the job, and is available almost everywhere you look. DRAM data resides in a cell made of a capacitor and a transistor. The capacitor tends to lose data unless it’s recharged every couple of milliseconds, and this recharging tends to slow down the performance of DRAM compared to speedier RAM types.

What is Dispatcher? - Dispatcher module gives control of the CPU to the process selected by the short-term scheduler; this involves: Switching context, Switching to user mode, Jumping to the proper location in the user program to restart that program, dispatch latency – time it takes for the dispatcher to stop one process and start another running.

What is CPU Scheduler? - Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1.Switches from running to waiting state. 2.Switches from running to ready state. 3.Switches from waiting to ready. 4.Terminates. Scheduling under 1 and 4 is non-preemptive. All other scheduling is preemptive.
What is Context Switch? - Switching the CPU to another process requires saving the state of the old process and loading the saved state for the new process. This task is known as a context switch. Context-switch time is pure overhead, because the system does no useful work while switching. Its speed varies from machine to machine, depending on the memory speed, the number of registers which must be copied, the existed of special instructions(such as a single instruction to load or store all registers).

What is cache memory? - Cache memory is random access memory (RAM) that a computer microprocessor can access more quickly than it can access regular RAM. As the microprocessor processes data, it looks first in the cache memory and if it finds the data there (from a previous reading of data), it does not have to do the more time-consuming reading of data from larger memory.

What is a Safe State and what is its use in deadlock avoidance? - When a process requests an available resource, system must decide if immediate allocation leaves the system in a safe state. System is in safe state if there exists a safe sequence of all processes. Deadlock Avoidance: ensure that a system will never enter an unsafe state.

What is a Real-Time System? - A real time process is a process that must respond to the events within a certain time period. A real time operating system is an operating system that can run real time processes successfully