open files etc. which have become

Hello hello I'm from Indonesia I know there is a problem how do I open the file again. etc that is so into the program C + + because I need the source code seems willing to help me thanks

Close the existing file (or stream). It is then possible to open it again.

If you want to open the file from two sections of code simultaneously (for example, two programs running at the same time, and both opening and reading the same file), then you usually need to use extensions specific to your operating system. Generally speaking, C and C++ standard libraries assume such sharing is not needed, although you can get lucky in some cases with some libraries (eg when both open streams are for read-only access).

That means no general code solution is possible. You need to read documentation for your operating system, compiler, and library and determine what extensions they support.