Was this the MS-DOS TSR app that kept running in the background and you could invoke at any time? Fond memories!
I was going to say the same thing. It had so many cool tools. A calculator, ascii chart, notepad, calendar. And the whole idea of a tsr opened a door in my head which hadn't seen multiple programs running at the same time till then.
That's the one. Nifty little program.
I thought of the phone with the spinning screen from the mid 2000s.