How to get Current Directory?

The question is not clear whether the current working directory is wanted or the path of the directory containing the executable.

Most answers seem to answer the latter.

But for the former, and for the second part of the question of creating the file, the C++17 standard now incorporates the filesystem library which simplifies this a lot:

#include <filesystem>
#include <iostream>

std::filesystem::path cwd = std::filesystem::current_path() / "filename.txt";
std::ofstream file(cwd.string());
file.close();

This fetches the current working directory, adds the filename to the path and creates an empty file. Note that the path object takes care of os dependent path handling, so cwd.string() returns an os dependent path string. Neato.

I would recommend reading a book on C++ before you go any further, as it would be helpful to get a firmer footing. Accelerated C++ by Koenig and Moo is excellent.

To get the executable path use GetModuleFileName:

TCHAR buffer[MAX_PATH] = { 0 };
GetModuleFileName( NULL, buffer, MAX_PATH );

Here's a C++ function that gets the directory without the file name:

#include <windows.h>
#include <string>
#include <iostream>

std::wstring ExePath() {
    TCHAR buffer[MAX_PATH] = { 0 };
    GetModuleFileName( NULL, buffer, MAX_PATH );
    std::wstring::size_type pos = std::wstring(buffer).find_last_of(L"\\/");
    return std::wstring(buffer).substr(0, pos);
}

int main() {
    std::cout << "my directory is " << ExePath() << "\n";
}