have放在句首,thanks..最好能够例子,

分两种情况吧，第一种就是上面两位楼主所说表示疑问
eg：have you seen my pencil?
第二种，相对要复杂些，表示虚拟语气
eg: have read the book , i would answer these questions
这句话的原句就是：if i have read the book, i would answer these questions.

Have you finished the homework?
你做完作业了没？

have 放句首表示 完成式疑问句
Have you seen my brother? Have you got a job? Have they watched the movie?
也可以表示“有没有”
Have you a brother? Have you any tickets?