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i want notes for programming 4*3 keypad using 8051 so can any one give some information about this .
You mean a keypad as for a telephone?
The one's I've seen have been very simple. Four wires across and three wires down; pushing a button makes contact on two of the wires, one for each axis. You can sense all seven lines on IO pins to determine which of the twelve buttons was pressed.
The data sheet for your keypad should document its interface.
If you're dialing a phone, then the wires also correspond to tones in the DTMF signalling. Usually this application would have a special-purpose DTMF generator device to make the audio tones, in which case you hardly need the microcontroller.