scanf: 1. input string may enter a number. 2, encounter a space to stop .3. There segmentation fault.
fgets: 1, only the input string. 2. Enter will stop. 3, there will be no segmenntation fault
scanf: 1. input string may enter a number. 2, encounter a space to stop .3. There segmentation fault.
fgets: 1, only the input string. 2. Enter will stop. 3, there will be no segmenntation fault