What is the difference Flex SDK and Flash builder?
please tell me about that....
Flex builder uses SDK to compile your data and create a swf. The SDK is free of charge but it means you have to do all your programming in some external program such as notepad.
Flash builder 4 and Flex Builder 3 are IDE but they are not open source and aren't free, so you will have have to pay or use a student license from adobe flash plattform.