Help needet with key bindings (especially to whitespace)

Configuration General Questions
1

I want to start a program (dmenu) when pressing + but I don’t know how to define this.

I found out that space has the keycode 65 using xev but i don’t know how to bind this in the config.

I now do know that I can bind the “Windows” key with

Key <some-key> A   4

But I don’t know why I have to use the “4” here. (Normally I use just an “M” to bind it to my ALT-Key).

It would be great if you can tell me where I can find more about these bindings and how to bind +…

Thanks a lot!

2 
Key Space A C SomethingToRun

See “xev” for how to get the keysyms.

– Thomas Adam