if you’re really using Notepad++ v6.8.6, that would have been from ~2015, which is an ancient version. Did you really mean v7.8.6, which is the current version? Going to the ? menu, and clicking on Debug Info and copying that into your reply will eliminate that confusion.

I am having trouble understanding what your problem is: I cannot tell for sure whether your code starts with the literal text algorithm, or literally ΑΛΓΟΡΙΘΜΟΣ, or what.

We cannot help you with compiler problems, if that’s where the problem is. But you seem to be guessing it is an encoding issue. Do your compiler settings have a way of selecting how the code is encoded when it reads the source code?

And without some underlying information, it’s going to be hard for us to remotely debug your possible encoding issues arising from Notepad++.

If I create a new file, change to Encoding > Character Sets > Greek > ISO 8859-7, then paste in ΑΛΓΟΡΙΘΜΟΣ and save, it creates a 10 byte file. If I drop to the cmd.exe prompt (File > Open Containing File In > Cmd or equivalent), I can display the file under my default code page (chcp) of 437 as ┴╦├╧╤╔╚╠╧╙. I then read through the Wikipedia article on code pages until I found one that displayed the file as expected (chcp 1253).

If I create a new file, set to Encoding > UTF-8, and paste in ΑΛΓΟΡΙΘΜΟΣ, I get a 20-byte file (which makes sense, because the Greek codepoints are encoded as two bytes in UTF-8). If I drop to the cmd prompt here, and chcp 65001 (which is the UTF-8 code page for Windows), it displays the file properly.

Could you show us which of those circumstances you are using for your file? Using cmd.exe screenshots of dir and type dumps under appropriate chcp will help us understand what bytes are in your file.

Alternately, If you are willing to install other programs, in the past I have grabbed the vim.org’s windows zipfile (gvim 8.2 link here), and I extract the xxd.exe into my path, so I can easily get the hex-dump of files in Windows; there are other hex dumpers available on Windows, but that’s the one I use. For the two files I just described, that gives me

D:\Users\Peter\Downloads\NppCommunity>xxd greek-19458.txt
00000000: c1cb c3cf d1c9 c8cc cfd3                 ..........

D:\Users\Peter\Downloads\NppCommunity>xxd greek-19458-utf8.txt
00000000: ce91 ce9b ce93 ce9f cea1 ce99 ce98 ce9c  ................
00000010: ce9f cea3                                ....

if you’re unwilling to download that, and don’t have another hex dumper, at least showing the cmd.exe screenshots similar to mine would help us debug your problem.