For the fourth year computer languages (java, JavaScript, c ++, etc.) people, they may have been confused NULL, empty, zero difference, here I describe what I understand:
If you check the dictionary to explain to NULL, the answer is likely to be zero, that is not the meaning, but it is the computer language, null is actually not a simple no, but even the air are absent,
NULL : for example, you move to a new home, Dad let you look at how much oil the kitchen, you go to the kitchen found that even drums are not, at this time how you answer, this time on the computer, it is null to represent.
The next day, your father bought a bucket of 5 liters of oil, at this time how much oil is 5L, on the computer, it is 5
Zero : After a while you run out of oil at home, this time, the computer, the oil drums that is 0
Empty : Your dad said that after use to buy oil does not taste good, put the barrel to clean your home, ready to buy some bulk oil refineries, oil drums at this time because nothing on the computer it is empty
Blank : in fact, the space is blank spaces between the quotation marks precisely or other invisible characters such as line breaks, tabs, line breaks, etc.