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;

Operating system

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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