I wanna see and learn the source of vanilla object, but I can't find the C source file.

I guess the C source of [metro] is metro.c, but metro.c file doesn't exist. I found it very difficultly named after x_time.c!

I guess:

[metro] is in metro.c

But actually:

[metro] is in x_time.c

How can I find the source of each object easily?

I would to know too, why and how naming the source file name? I can't understand...

Thanks,

akntk