It depends how complicated you’re going, it’d be easier to recommend if you had a specific project in mind. You could make a simple ‘GUI’ that just opens in a CMD/Terminal window with C++ and easily allow input (cin), changing what’s displayed as you desire. You could easily do your example this way, without the need of anything overly complex.
In terms of using Notepad you probably want something with at least some sort of formatting to make it a bit easier on yourself (such as Notepad++) although you could just open Notepad and start coding. There are IDEs such as Eclipse with the CDT plugin which are good for starting C++, or Visual Studio. I’m not big on Javascript myself, but I’ve heard Komodo is good for web coding.
In terms of complex GUIs, as has been said in the comments there are many and it basically comes down to your preference as to which you use.
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solved Where do I start for writing my own calculator program [closed]