why there are so many tty files in the dev directory?

Question

it is confusing that there are so many tty files in the directory...

by the way, what each file in /dev stands for, do they stand for physical devices which are part of my android device? for example, which file stands for the raw storage device in /dev directory?

Answer 1

Not all devices at /dev are physical, some of them are logical and may be temporary needed by kernel/software (and some of them are symlinks, like log_modem -> /dev/ttyACM2). And, as I see, you have default linux tty count. It's not used (reserved and may be used), but it's no problem.

Answer 2

That's because there are so many devices available. Entries in /dev are not restricted to physical devices, but also include logical ones. You just named one: TTY. You don't really think you've got 63 "connectors" somewhere to attach keyboards etc. to? Also, /dev/random is nothing physical, but rather "software" (a random-number generator provided by the system itself). Same applies to things like /dev/null, /dev/zero, and several others.

For more/deeper details, you might refer to following articles:

• Linux Filesystem Hierarchy
• Device file (Wikipedia) -- recommended for this topic, as it explicitly included Pseudo-devices
• Linux System Administrator's Guide - The / dev directory