Atari  

The more active answer and current standard is to atari at . After Black plays a or b to keep White pressed down to the top side, or c to take positions on both sides at the expense of the corner.

A - Influence and sente  

The hanging connection of aims for influence and sente. It leaves the corner for White to take sente once more:

A - Influence follow-up  

White gets a nice corner but Black got 2 moves elsewhere.

B - stressing the corner  

When Black holds back to this solid connection, he can revert to the previous variation, but also decide to take the corner with . Next White usually continues at and Black can exploit the aji at a, which leads to a longer fighting variation.

C - developing on both sides  

Black can push through at if there's support on the upper side for the fighting that will occur due to White's cutting stones.

C - White sente  

White can also choose to capture the corner directly at . This gives Black a thicker influence but after -, White can take sente.

Other variations

Bulge play for ko  

Playing the bulge for ko is locally bad for White. Black will take and it will require a good ko threat to get advantage out of it. As this is an early corner pattern, such big ko threats are rather rare.

Contact  

Hoping someone can say why white playing is a bad move please.