about vim dd dw dl

each time ,when I delete some code,the copy buffer will be replaced by the deleted word.
for example:
1 #if 0
2 #include <stdio.h>
when I move to 1,press [yy],vim will copy this line to buffer,when I press [p],line 1 will be paste ,
but if I move to line 2,use [dd],the line 2 will replace the line 1 in buffer,and each time I press [p] key,line 2 will be paste,

I just want to paste line 1, how to configure it ?(my enviroment is fedora 15)

That is because in vim dd is equivalen to "cut entire line" while yy is "copy entire line". delete a line without editing the buffer you can use the following sequence: "_d
note that the quotationmark needs to be there (this selects the buffer you want to use)