JavaCard OS

Hi, I am just starting to study java card technology and I am using JCIDE to debug a simple "helloworld" java card applet. When I sent SELECT command to it, it returns 90 00, which is a status word. But I have viewed the whole code, there is no 9000 at all. So who sent this status word? JCIDE or others? Thanks

By default, it automatically replies 0x9000 unless it hits an error or you tell the code to send some data or status words you designate.