Writing into specific place in file (C++)

Hi,
I am trying to figure out how to read and write from files using ifstream and ofstream
I use
seekp() to get to the needed position in the file
put(), write() or << to write into the file,
but as a result I get the data in the right place, but everythin else is empty spaces, all other text from the file disappears.
I used ios::ate to disable default ios::trunc in construction.
Maybe some other flag chould be used?
Anyway, I need help on the topic and maybe a link to the complex example on reading and writing to files (and not only appending at the end)
Thanks

Hi,

Do not use ios::app.
Use seekp to go to the specified location.
Save the contents from the specified location to the end of the file in a buffer or else it will be overwritten.
Write the data in the specified location.
Write the saved data from the buffer to the file.
Thats it ...