I got upset. My MacBook Air was suddenly crashed and I had to wait for a long time to boot it again in a cafe.
I had tried to plug an ear phone into my MacBook Air. Look at this figure:
We cannot see these ports without putting up MacBook Air very high. Therefore we have to plug an ear phone into it without seeing there. The worst trap with MacBook Air is that if we plug an ear phone into the very neighbor USB port, the machine will be crashed just at the time. There's no warning nor alert.