adj.无效的；无价值的；无效力的
n.零；空
vt.使无效
Their actions rendered the contract null and void. 他们的行为使合同无效。
The marriage was declared null and void. 婚姻已宣告无效了。
用作名词 (n.)The path must end with a null character. 该路经必须以零结尾。
A null reference pointer was passed to the stub. 向占位程序传送了空的索引指针。
Primary keys do not allow null values. 主键不允许空值。
