terminal.cpp: Version for running from the Command Prompt / Terminal (naming depends on OS)
Dockerfile: File to build the docker image.
### How to build
#### Regular
First, ask this question. Are you going to double-click this in the file manager / on the desktop or type `calc` in the command line to run it? If you are gonna use the command line, use terminal.cpp. If you are going to use your file manager / the desktop, use main.cpp.
Windows:
`g++ <main.cpp / terminal.cpp> -o calc.exe`
To run it, type `calc` at the prompt, or double-click the executable.
Linux / macOS:
`g++ <main.cpp / terminal.cpp> -o calc`
To run it, type `./calc` at the prompt, or double-click the executable.