Hex key pad or matrix key is a way framing the input switches. Any number of matrix can be framed for interfacing the switches. 4x4 matrix keypad controls totally 12 keys in it. It has 3 columns and 4 rows in the boards. I-labz 4x4 matrix keypad has 8 pin connector for 4 pins are treated as input & other 4 pins are treated as output.