opening serial monitor

Hi, I'm running cygwin with netbeans to compile my arduino software. However, I am using the serial monitor that comes with the arduino IDE.

When this monitor is opened, what exactly happens? Does it reset the program to start over?

Also, does replugging the usb cord have a different effect than just pushing the reset button manually?

Does it reset the program to start over?

On an un-modified Arduino, it does. Opening or closing the Serial Monitor window sends a reset signal to the Arduino, causing it to reset.

Also, does replugging the usb cord have a different effect than just pushing the reset button manually?

Connecting the USB cable causes the Arduino to reset, but it also tells the PC that a change has occurred, which may cause the PC to do stuff.

Pressing the reset button on the Arduino causes no communication to the PC. It just resets the Arduino.

Not sure what your hardware knowledge is like (or which Arduino you're using), but if you look here: http://arduino.cc/en/uploads/Main/arduino-duemilanove-schematic.pdf you can see that the DTR (Data Terminal Ready - a throwback to RS-232 serial physical protocols) line from the serial line chip is connected to the AVR's reset pin. Here's a whole lot of stuff on the subject: http://www.google.com/search?ie=UTF-8&oe=UTF-8&q=DTR+reset&domains=http%3A%2F%2Fwww.arduino.cc%2F&sitesearch=http%3A%2F%2Fwww.arduino.cc%2F

Okay thx

uhm, I actually had 2 arduinos connected to the same pc, but I guess opening a serial monitor for 1 of them, actually resets both?

Yes I people have reported that here, it's a function of the PC operating system and the drivers.