You can enter any ANSI character into a Windows application. If you see it on the keyboard, just press it. Even if it isn't on your keyboard, you can still enter it using a special Alt-Num key sequence.
Unfortunately, this ANSI character set is incompatible with the ECS character set used by DOS. For example, the British pound symbol is code 163 in ANSI, but code 156 in ECS. Worse still, ANSI does not include many of the ECS symbols, particularly the line drawing characters. If you try to display a DOS document in Windows, Windows attempts to convert the ECS characters to ANSI. Any character that does not convert is replaced by an arbitrary graphic. Therefore a round-trip conversion from DOS to Windows and back will not re-create the original document.
Windows NT uses the 16-bit Unicode character set, which covers scripts in use by major living languages, including the far east, plus dead languages which are in widespread scholarly use. Windows 95 still uses the 8-bit ANSI character set, but is a transition toward Unicode (32-bit OLE uses Unicode and Cairo includes some Unicode as well).