Tenshi the AI – Round 2
Maeno posed a question in Raph’s most recent post on Angel Beats. Why didn’t Yuri just delete Angel’s program? Wouldn’t that have solved the problem immediately? The short answer to this question is she simply can’t do it. I could just leave it at that, but it doesn’t really explain anything about the underworking technology. If you’re prepared, click past the break so I can give you a little lecture on some basic computer theory.
You are not prepared!
Computers do not work as basically as most people think. This is due to the wonders of abstraction. You don’t actually need to know how the components work to operate a computer. In reality, we could divide a program’s execution into three layers. First, we have the place where we store all of our data. For most people, you would use the hard drive. Then, we have volatile memory, or RAM, which holds program and document information fetched from the hard drive. Finally, we have the processor, which performs operations on data stored in the RAM. Because of this layering effect, most operating systems “pin” data when it is stored in RAM so you can’t delete it. Why?
Well, the first reason is obvious. RAM is separate from the hard drive. Thus, if data is already in RAM, deleting it from the hard drive doesn’t accomplish anything. You can see this in action for yourself. Simply open a document in your favorite word processor, and then try to delete the source file. Your computer will tell you it can’t do it, probably with a message saying the file is in use.
The second reason is a bit more complicated. You see, the computer only allows a program to use a finite amount of memory, even if more is available. So, when you run a program, it won’t all be in memory all of the time. On occasion, the processor will have to swap two segments of the same program to continue executing. Now think about what would happen if you deleted a running program. When the processor tries to make the switch, there’s no data to swap in! At best, the program would crash, and at worse, it might try to continue executing with bad data. Now think about how Tenshi is a melding of humanity and technology. Do you really want to find out what happens when her ANGEL program is deleted while running?
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This explains why Yuri doesn’t delete anything. However, a sharp reader might wonder how Yuri can add to the program. After all, it’s pinned down to the drive, right? Well, there are languages that allow you to edit the program while it executes. You can delete, change, or add to the code even though it’s running. This does not stop you from causing errors, so you have to work with caution. Yuri cannot delete or edit any code for that reason: she has no idea what will happen. Specifically, she can’t read English. Thus, she can only add to the program. So long as her addition will not directly interfere with other functions, she shouldn’t have a problem. Yuri types in a timer routine and links it to the program, and everything checks properly.
Now, I’m trying to explain this all off the top of my head and in very basic terms, so this still isn’t exactly how the computer works. I simply present this as an illustration for why Yuri does what she does. Hopefully, it makes more sense now.
Of course, she still screwed up, so... yeah.
