Why does my iPhone device not show up on any computer?

When I used to plug my iPhone into a computer, the device would pop up on the computer screen automatically, or show up in the "my computer" folder and I was able to upload and edit photos saved in my phone, without the use of iTunes. This no longer happens. Now all the phone does when plugged into a computer is charge. What do I do? I do not know whether it is the public computers I'm using or my iPhone itself? I'm unable to use my own laptop because it is broken. Help Please! >_<

Added (1). I can use my flashdrive device on these computers (most are of colleges, universities, and a friend of mine's), which can upload the same stuff… So what's the difference? And I said that I used to upload from my iPhone before, which was only some months ago… I don't think a restriction would have been put on that quickly, do you?

Public computers.

There's lots of malware out there. Much of it tries to use exploits found when "auto play" is used. Much of it is transferred from external storage devices (like small USB drives). Because of the virus/malware possibilities, the default for auto play or mounting an unknown external mass storage device *should* be "do nothing".

From my view, all is working correctly. The folks who own the computers are doing the right thing by limiting this access. So when you get your computer fixed or replaced, you won't have this issue anymore because you can configure your computer to do what you need/want…

Thank the people who write/distribute virus/malware for this "limitation" you are experiencing.