Content-Type: text/shitpost


Subject: Stuff that didn't work
Path: you​!your-host​!wintermute​!gormenghast​!qwerty​!fpuzhpx​!plovergw​!shitpost​!mjd
Date: 2018-07-26T16:44:37
Newsgroup: misc.didnt-work
Message-ID: <29a9afd1c30ddafd@shitpost.plover.com>
Content-Type: text/shitpost

I want to use this story in a future article about novices with inaccurate mental models.

When I was a young teenager, I had a Commodore 64 computer. It could do bitmapped graphics. You would tell it which pages of memory should be displayed on the screen, and then poke bytes into that region of memory to switch the dots on and off. I had a lot of fun with this.

I did not have a dedicated monitor. Instead I had an old color TV that the computer used as a display. There was a device on the back of the TV that switched it between displaying the computer output and displaying the received TV signal. One day I had a wonderful idea: I would switch the device to TV mode and put on some TV program — I imagined Star Trek specifically. Then instead of poking data into the computer memory to make dots appear on the screen, I would read the memory into a file to get a screenshot of the TV program.

I didn't expect that this would work well; I thought if it worked at all there would be a huge amount of sampling skew, because the TV image would change drastically during the memory copying process. But I hoped the results might be interesting anyway, and at least part of it might be partly recognizable.

Of course, it didn't work at all. The connection from the computer to the TV was entirely one way. The device on the back of the TV was an RF modulator, which transformed the computer's video output into a fictitious radio signal that the TV would interpret. Switched into the TV position, the computer's video output went nowhere. In no case was the TV image accessible to the computer. My program to read the contents of the bitmapped memory read nothing but zeroes.

I think it's useful to remember times like this when I was so utterly confused about what was really happening.