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I Don't know the meaning of this code in bold, please help. I do know about the file handling but not about the sizeof() function etc. please help!

C++

void function()
{ofstream o;
	char ch;
o.open("abc.txt",ios::out|ios::app);
	do
	{
		system ("cls");
		bk.create_book();   //create_book is a function in the class by the name of "book"//
		o.write((char*)&bk,sizeof(book));     //bk is an object of the class "book"//
		cout<<"\n\nDo you want to add more record..(y/n?)";
		cin>>ch;
	}while(ch=='y'||ch=='Y');
	o.close();
}

Posted 10-May-12 6:57am

ShayanTanwir

Updated 10-May-12 8:20am

v3

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3 solutions

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Aescleal · Answer 1 · 2012-05-10T07:34:00

The short answer is something you shouldn't do in C++ unless you really know what you're doing, and even then there's usually a better way.

The long answer is that it's writing the block of memory containing bk to the file "abc.txt." Which hopefully isn't something you're going to want to edit with notepad as it sure as hell won't be a text file after a lump of any old rubbish gets written in there.

Cheers,

Ash

PS: Really, don't do it...

PPS: No, take your hands away from the keyboard unless you're going to delete that lump of code...

CPallini · Answer 2 · 2012-05-10T10:07:00

Solution 3

The bold line is doing 'poor-man' serialization. the sizeof operator is (surprisingly!) documented, see, for instance MSDN[^].

Posted 10-May-12 10:07am

CPallini

Comments

Sergey Alexandrovich Kryukov 10-May-12 16:26pm

Right, a 5.
--SA

JackDingler · Answer 3 · 2012-05-10T08:51:00

Solution 2

sizeof() operator returns the size in bytes of the object you pass as a parameter.

Posted 10-May-12 8:51am

JackDingler