wincvs中用add命令出错?????

tomylinux

选中一个文件,点击菜单
Modify==>add
出现如下错误
cvs add -- test.txt (in directory D:\cvs\)
cvs add: No CVSROOT specified!  Please use the `-d' option
cvs [add aborted]: or set the CVSROOT environment variable.

***** CVS exited normally with code 1 *****

什么原因呢???