on basic resitor activity

[Bhuvanesh Nick]

what is pull up resistor and pull down resistor.where it is used.Explain me basically

 

[davoud]

Pull-up & Pull-Down resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected or high-impedance is introduced.
See This link : https://en.wikipedia.org/wiki/Pull-up_resistor

 

[jiripolivka]

Generally, some logic circuits have an output stage made of a transistor, with its collector connected to the output pin. To make a fully operational output circuit, one needs a "pull-up" resistor connected from the output pin to the Vcc, or the positive power supply line.
Other circuits require a resistive load connected to ground line, this is called the "pull-down" resistor.