See infinite8s' post above. The "Engelbart's demo" mentioned is called
The Mother of All Demos, which you can find by that title on youtube.
I have to admit I never really got further than the first 5-10 minutes or so. My first computer experiences are from the late 80s (and indeed didn't have a mouse) but this demo is so old, I kept having to mentally translate for myself which bits might have been new or ground breaking, and which just plain archaic. I keep meaning to watch it in full some day, but the first bit that I saw, I keep feeling I'm missing something important. People are lyrical about this demo (hence the name!), but I don't quite feel it or something. Then again, while I appreciate the great work of engineering that went into it, I'm not really one to sit down and watch a documentary about the moon landing program either.
Maybe somebody here knows a good link or article about The Mother of All Demos that explains which things I should be in awe about and why they were so novel then?
Part of it kind of looks like a simple database table system, which reminds me of a stupid story from my childhood. When I was young (~1990 I guess), I was playing with the MSX BASIC on a friend's computer whose family had a farm. They wondered if I could write anything to keep track of their cows or something--sure thing! (though I really preferred to write graphics code, later joined the demoscene, way more fun). Now I had no idea about business or their requirements (let alone requirements engineering), so I just wrote some whatever that let them enter data, but in the back of my mind I wondered how this was going to be useful for anything. Neither did I know (yet) how to actually save the data so it'd be available after reboot, which was probably a big reason for my doubts. And they were still impressed (that it could repeat names of many cows, I guess). I never finished it (nor any idea of what "finished" would mean).