Every time a key is pressed on a regular keyboard, a numeric 'key code' is sent to the computer, eg. 32 or 51 which represent specific keys.
Unrelated to my default keyboard which I am using to type this post, I want to be able to plug in a keyboard via USB and have its key codes all shifted up by some constant C.
Thus, when pressing the 'a' key on this side keyboard, the computer would not receive the keycode for 'a', but rather some higher number which the computer does not have a planned response to.
These out-of-conventional-range keystrokes will control a program of mine which knows what they are and will be listening for them.
Hardware or software solution would work for me. Perhaps there are special keyboards sold for this end, or maybe some software-related modification could let this be accomplished for any regular keyboard– I have no idea. What is crucial is that the keycode shift applies only for my side keyboard and not my default keyboard which I use for regular stuff.
Edit: I'm on Windows.