ARDUINO MINI PRO
The Arduino Pro Mini is a microcontroller board based on the ATmega328.It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, an on-board resonator, a reset button, and holes for mounting pin headers. A six pin header can be connected to an FTDI cable or Spark fun breakout board to provide USB power and communication to the board.There are two version of the Pro Mini.One runs at 3.3V and 8 MHz, the other at 5V and 16 MHz.
The Pro Mini is not physically compatible with Arduino shields (you could still hard-wire the Mini up to any Arduino shield).The Pro Mini uses the same ATmega328 and also has same 14 digital i/o pins,6 analog pins as in Uno. Though it differs from Uno by some hardware changes such as,Size-Pro mini is just 1.3x0.70" and it is about 1/6th the size of the Arduino Uno,Operating voltage-Pro mini has only one regulator on board either 3.3V or 5V unlike Uno which has both 5V and 3.3V and the Clock Speed is 8MHz fro 3.3v model which is half the speed of Uno.