New to foundation class : CArchive

I use CArchive to store a string
into a file

But I always get an odd character (a square shaped) on top of the file,
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Cfile f("t.txt",Cfile::modecreate|cfile:modewrite);
CArchive ar(&f,carchive::store);

Cstring s="show me the square";
ar<<s;

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Could you help me please ? :(

Thank you

CArchive doesn't write text files. It adds other information in there. Use CStdioFile if you want to write plain text.

When writing a CString with CArchive, the length of the string is also written to the file. This is done so that the CArchive::Load will know the size.

If you have MBCS character set used, you'll see the length as the first byte (if the string is less than 254 characters) - so that's the square that you see.

There is no need to over complicate the things. Use CStdioFile.