Is it possible to connect many arduino uno in one pc?
Yes, you can connect multiple Arduino UNO (USB) boards to a single PC. There's a simple way and a more advanced way to manage it.

The simple way is, having multiple boards plugged in, but using only one Arduino Software IDE to control one board at a time. (IDE = Integrated Development Environment. Some elements of the Arduino system use non-standard technical terms.) Use the Tools &gt; Port menu to select which one of the attached boards to control. The selected board type and port appear in the lower right status bar.

A more advanced way to manage multiple boards, is to open multiple Arduino Software IDE instances -- each instance has its own independent Tools &gt; Port setting. You could then edit, verify, and upload two different "sketches" (programs) to two different boards, without losing your place and without having to constantly change the Tools > Port setting. This would be convenient if you were developing a communications protocol between two or more boards.

This multiple-ports technique won't work unless you launch another instance of the Arduino Software IDE, without closing the first one. It isn't enough to use the File menu to open another window, because then you just get another window that shares the same Tools &gt; Ports setting. Changing the ports setting on one window, changes the setting on all of the windows that belong to that instance. To support multiple boards at the same time, you have to actually launch the Arduino Software IDE again, without closing the first one, to create a second instance.

Usually you'd expect each window would represent a unique document, and they'd all be related to the application. But Arduino Software IDE has a hidden dependency between its windows. Whenever you restart the IDE, that opens a new and invisible instance of the IDE, where it remembers the board and port settings. If you use the File menu to open a new window, that new window is still part of the same IDE. So changing the Tools &gt; Port setting on one window, changes that setting for all of the windows that belong to that instance of the IDE.

But if you restart the Arduino Software IDE (e.g. Windows Start Menu > Arduino-1.6.0), without closing the previously opened IDE, then you get a second instance. If you pay attention to the port setting visible on the lower right status bar of each window, you can distinguish which windows belong to which IDE instance.

Each time you launch the Arduino Software IDE, you start a new instance of the software, that can talk to one board. Each instance of the IDE can have an unlimited number of windows, but they all share the same Tools > Port setting. If you re-launch the Arduino Software IDE again without closing it first, then you get a second instance that can have a different Tools > Port setting, and thus control another board at the same time.

Verified on Windows 7, Arduino Software IDE 1.6.0, with two Arduino UNO revision R2 boards (firmware rev 0001), Arduino device driver 1.0.0.0.