KEYPAD in AT89C51

Keypad is a switch group which consist of columns and rows. Keypad have a good characteristic that is a rows and columns can not change.
In process writing and sending data keypad working use 2 method that is method scanning and method polling. Keypad in AT89C51 use scanning method the function is menerima input keypad button and a bring digit or character to instrument a bring such as 7 segment or LCD. Keypad use resistor pull up.