why doesn't his code work ?

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require 'net/ftp'
ftp = FTP.new('www.aaa.com', 'xxx', 'xxx')
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it gives this error:

C:\ruby\bin>ruby "C:\Documents and Settings\Administrator\Desktop\radio.rbw"
C:\Documents and Settings\Administrator\Desktop\radio.rbw:3: uninitialized
constant FTP (NameError)

The class in the net/ftp.rb file is called "FTP"