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Hi everyone.



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So from this lesson we will start learning file handling in C++.



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Now in this world we will learn this topic writing to a file.



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So for writing to a file the syntax.



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What do you have to lose so for writing the code.



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First of all you have to include a file and the name of the file is f a stream file stream so after



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including the file so it is obvious that we will write the code inside me.



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Then what we have to do so the name of the class is o f stream output file the stream.



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So this is a class.



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And what you have to do is we have to create an object.



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Let's say the name of the object is output file.



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I would file is the name of the object.



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And so what this object will do.



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I am calling a constructor so for calling the constructor you have to give a file name so I'm giving



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the file in my final dirty.



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So suppose there's a file and the name of this file is my file in my file dart the 60 so after writing



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this piece of code what will happen.



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So there is a connection between this object and this file.



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So a connection will get established between this object and this file.



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So basically you will do anything with this object.



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Then the changes will get reflected inside this file.



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So whatever you're going to do with this object the changes are going to be reflected in the file.



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My friend not the extreme.



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Now there are two things that can happen.



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So after writing this line.



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So when you will write this line then you will execute this line.



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There are two possible situation.



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So the first situation is this file already exists.



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This file already exists.



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So what this statement will do.



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So this statement will open the file.



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So if the file already exist then open the file then open the file.



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Now the second situation is this file does not exist.



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So if this file does not exist then this piece of code what will do with this line what it will do.



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It will create the file.



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So it will create file with the name my file not the 60s.



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So I'll finally be created with this name my file not the 60 and then open that file.



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So cleared file and then open that file so cleared file and open file.



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I'm everything myself.



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So this line can do two things.



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So if the file already exists.



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So if this file already exists then open the fight.



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And if this file does not exist then basically cleared the file with this name.



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My file not the 60 and then open that file simple.



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Now let us discuss next thing.



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So what can happen.



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So for example this is your file.



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My file not the 60.



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So basically if you will do something like this Let's say you are trying to write something to a file.



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So if you do this out file you want to insert you want to write Hello world inside this file hello world.



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And Andy.



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So what will happen the effect of this line is go to the file and write Hello world.



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So this file can be empty so the first scenario is this file can be empty.



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The other scenario is this file list containing some data



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so this file might be containing some data so if you execute this piece of code.



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So if this is the situation then obviously what will happen.



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So Hallowell will get printed here.



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Now if this is the situation your file is already containing some data then what this line will do.



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So this line will actually truncate.



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So this line will actually delete all your data and then it will insert Hallowell so all the data will



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be deleted and then this string will get inserted.



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Now if you want to preserve the data if you want to preserve your oil they don't you do not want their



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oil later to be removed.



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So what do you have to do you have to pass of one what barometer in the constructor.



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Basically we have so the second parameter can be.



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So we'll hear what I'm doing.



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I am writing off a stream then the name of the object is out file the name of the file is my file not



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the 60.



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Now the second barometer can be one of the two things.



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So the second parameter can be us.



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Column Column D R U N C so D2 and C means truncate.



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So this is by default if you will not give the second barometer then this is the second barometer by



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default.



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And if you want to preserve the content.



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So if you want to preserve the content do you have to write something like this.



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IOW column Column B so APB stands for append the data so this all thing is Same here.



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So there are two types.



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So the second parameter can be truncate.



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So this is by default.



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So I have not written truncate here.



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So what this line will do if you want to insert something into the file it will delete your all data



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and then it will insert Hallowell.



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But if you want to preserve the data if you want to preserve the data then you have to write a US column



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column append.



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So what will happen if a file is already containing some data then Hallowell will get inserted at the



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end.



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OK.



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So by default this is truncate and if you want to present the data I will use append APB.



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So this is just an index for driving data to a file.



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Similarly you can write more data.



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For example you can write out file.



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Let's say you want to insert it in teachers or you can write.



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I would file 50 and line similarly.



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You can write it like this.



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I would file.



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Let's say you want to insert the branch of the student so you can insert CSC and line.



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So in this way this is this index for writing into a file.



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Now after writing to the file after your work is or what.



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The most important thing that we have to do is basically close the connection.



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So you have to write you have to call the function dot close.



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So the name of the function is close.



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So after doing all the work that you want to do with the file you have to call the function goes.



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So what this close function will do it will.



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So this is the connection so this connection will get a break.



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This connection will be broken if you will call the function close and it is very important.



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It is a very good practice also and it is very important also to call the function close.



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Now what will happen if you will not call this function.



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So why this function is important why calling of this function is important.



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So you have seen many times for example when you connect pen drive to be a computer and then if you



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want to eject to a pen drive.



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So after connecting the bend over to a computer if you want to eject you up and drive then sometimes



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an added pop ups that some program might be using this pen drive.



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So you can not eject and that is because of this thing.



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So the developed but forgot to write this line output finally got close.



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So that's why the connection is still there.



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So if the connection is it still did if the connection is still there then you will get this idea that



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some program is using your pen drive.



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So you cannot eject.



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So what you're doing those scenarios you basically lose that program.



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So if the program is closed then what will happen.



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So this connection will be broken disconnection will break.



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And you can eject you up and drive.



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So it is always a good practice after your work is done with the file.



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You have to call the closed function so in the next we do we will write the code.



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I will see in the next one maybe.