Keypad is a widely used input device with lot of applications such as telephone, computer, ATM, electronic lock etc. A keypad is used to take input from the user for further processing. Here a 4 by 3 matrix keypad consisting of switches arranged in rows and columns is interfaced to the microcontroller. A 16 by 2 LCD is also interfaced for displaying the output. The interfacing concept of keypad is very simple. Every number of keypad is assigned two unique parameters that are row and column (R, C). Hence every time a key is pressed the number is identifying by detecting the row and column numbers of keypad.