Code Question

[Scale]

How would i go about and find the code for repressing for example:

In most games when u shoot a pistol it will fire only once till u press it again,

or Quake games where if u press and hold space in mid air u will automaticly jump again once u hit the ground.

but then wont jump again unless u release and repress space.

Dont know how i should look for it :X

Thanks for the help.