Here are the parts of the metal face of the sim card:
VCC: Power supply input RST: Used itself or in combination with an internal reset control circuit. CLK: Clocking or timing signal GND : Ground VPP : Programming voltage input I/O : Input or Output for serial data to the integrated circuit inside the card.
***Some Sim Card have C2 (Reset) and C6 (VPP) active, While C4 and C6 are used as USB Inter-chip
RESET: Either used itself (reset signal supplied from the interface device) or in combination with an interal reset control circuit (optional use by the card). If internal reset is implemented, the voltage supply on Vcc is mandatory
VPP:Programing voltage input (optional). This contact may be used to supply the voltage required to program or to erase the internal non-volatile memory.
USB Inter-chip: May be used to store extra information.