It runs because you've table 'abcd' on the path on your computer which the USE command opens, not the cursor 'abcd'. Run following code to see for yourself

CREATE CURSOR mytable ( id int, cc C(10))
SELECT * FROM MyTable ;
	INTO CURSOR abcdzzz NOFILTER
USE abcdzzz ALIAS qwer IN 0    && Error

USE DBF("abcdzzz") AGAIN ALIAS qwer IN 0    && Runs fine

>I used the first one and run very well
>
>USE abcd ALIAS qwer IN 0
>
>just wonder should I change because it already installed in the client site.
>