Basic Guide to Use a Keypad
A keypad is one of the most commonly used input devices in microprocessor applications. In a standard keypad wired as an ROW-COL switch matrix, switches connect a row to a column when pressed. If a keypad has 12 keys, it is wired as 3 columns by 4 rows. A 16 key pad would have 4 columns by 4 rows. Keypad Applications
A keypad can be used in projects where you need an entry of numbers, letters or characters, a key would be a keyboard, mobile phone, enter a password, etc.