on a UNO ,what are these for ? another icsp connection or what ?
and a four holes with J2 what are they for ?
It sounds like you have an Uno R3. The reset button was moved between the R2 and the R3. The 6-pin header near the USB port is for ICSProgramming the ATmega16u2. This chip has a bootloader, so it can also be programmed via the USB port. The 4 holes marked J2 connect to various port pins on the 16u2, which can be useful if you ever want to do more than USB-to-serial conversion with this chip. Some time ago I wrote some code which allows the 16u2 to work as an ICSP programmer, meaning you could update the Arduino bootloader without needing a second Arduino. I used one of the J2 pins to switch the software between USB-to-serial mode and ISCP mode.