could some 1 do a justice to this question

[yanda]

please what is pull-up and pull-down resistors and what exactly is there function in a circuit

 

[barry]

Generally, they are used to pull an input to a known state when there is no driving signal.

But they do have other uses.

 

[picgak]

pull up means resistor from output point to +ve, pulldown means resistor from output point to -ve .The condition when no output is awailable at the output point , your pulledup+ or pulldown - will prevail