It"s amazing how many people assume I"m computer-illiterate and then take cheap shots. FWIW, I started with a ZX-81, loved my BBC B and have stayed in touch with computing since, including a stint working on embedded control and launching some quite successful products of my own design. PICs, for instance, whilst somewhat simpler than the R-Pi, hold no fears for me.
The thing that is coming over to me from replies to my original post is that ther are many who want to show how superior they are by making snide comments, including "the information you want is on the Forum". Clearly, they know where, but are protecting their superiority by not telling anyone else.
Take the issue with the too-small image surrounded by a sea of black. Eventually, I discovered that the magic word was "underscan" and that I needed to edit a file called "config.txt" (not, as one poster unhelpfully said, config.tx, and pointing people to a link that doesn"t exist). Eventually I discover this should be in a folder called /boot (from one forum area) and (from another forum area) that it needed some empirically-derived numerical values.
I searched, but the file didn"t exist. I tried using Leafpad to edit and save a suitable file, but I wasn"t allowed to save anything in that folder (why not? it"s my computer!). Then, on yet another forum I discover I can do this with my PC and Notepad. So it"s back and forth to my PC with the SD card, finding appropriate values. Now, I"ve got a working display that fills the screen.
Wouldn"t it be helpful if someone, somewhere, wrote something like this:
You"ve probably noticed that the R-Pi graphics don"t fill tha 1080p (ie Full HD) screen. This is due to something called "Underscan", and it can be fixed easily by creating a simple text file on your PC. Here is what you do.
1. Shut down your R-Pi, remove the power and remove the SD card.
2. Put the card in your PC"s card reader and browse the contents. There should be some text files and others that the PC doesn"t recognise. That"s fine.
3. Look to see if there is a file called config (or possibly config.txt). If there is, open it with Notepad. If not, create the file with Notepad.
4. Type the following:
Then save the file.
5. Take the SD card out of the PC, put it in the R-Pi, and power up the R-Pi. You should see that the graphics area has increased, but probably won"t fill the whole screen.
6. Making the R-Pi graphics fill the screen is a matter of adjusting the numbers you put in the config.txt file. To do this, shut down the R-Pi and edit the config.txt file as described above. Change the numbers - try jumps of 5 or 10 at a time. Bigger negative numbers reduce the black borders (so -48, which is what I use on my system means less black border than -20). The numbers do not have to be the same - you can use this to centre the display on the screen.
OK, so maybe the above isn"t technically 100% but it"s an awful lot more use to an ABSOLUTE absolute beginner than "look at the forums" or "watch a video".
Just my 2p worth.