C++ - Printing copyright symbol © displays reversed not sign ¬

Your text editor is likely using one of the following character encodings: Unicode (usually UTF-8), ISO-8859-1, or Windows CP-1252.
Unicode is based on ISO-8859-1, which is itself based on Windows CodePage 1252, which is why they are all similar.

In all of these character encodings, the copyright symbol is encoded as: hex A9, Octal 169, or Decimal 251.

The default CodePage for a console application is 437.
And in CodePage 437, the character at hex A9 / Octal 169 is ¬. The reversed not sign.
CodePage 437 has no copyright symbol.

And that's the problem. Your text editor is using one encoding, an encoding that does support the copyright symbol, and the console is using a different encoding. One that does not support the copyright symbol.

We can confirm this by modifying the program to print the active CodePage.

  int main()
  {
      auto cp = GetConsoleOutputCP();
      printf("Current codepage is %d\r\n", cp);
 
      char* copyright = "Copyright ©\r\n";
      printf(copyright);
      return 0;
  }
  

CodePage 437 is designed for DOS console applications, which is why it has 48 characters for drawing lines and blocks.

We can fix the problem by changing the console CodePage to 1252:

  int main()
  {
      SetConsoleOutputCP(1252);
 
      auto cp = GetConsoleOutputCP();
      printf("Current codepage is %d\r\n", cp);
 
      char* copyright = "Copyright ©\r\n";
      printf(copyright);
      return 0;
  }
  

Alternative fix #1. Write Unicode to the console using _setmode(_O_U16TEXT) and wprintf():

  int main()
  {
      _setmode(_fileno(stdout), _O_U16TEXT);
      
      wchar_t* copyright = L"Copyright ©\r\n";
      wprintf(copyright);
      return 0;
  }
  

Program output:

Alternative fix #2. Write Unicode to the console using WriteConsoleW():

  int main()
  {
      wchar_t* copyright = L"Copyright ©\r\n";
      auto handle = GetStdHandle(STD_OUTPUT_HANDLE);
      WriteConsoleW(handle, copyright, wcslen(copyright), NULL, NULL);
      return 0;
  }
  

Program output: