my computer os is window vista, i create a java program using the notepad but i can't compile file and run the program output in command prompt.
when i compile the file: javac welcome.java
'javac' is not recognized as an internal or external command, operable program or batch file.
it is my computer setting something wrong?

I definitely saw this exact same question answered here on daniweb in this forum within the last 6 months. It seems pretty obvious why you're getting that error (since, in fact, the error itself explicitly says why you're getting it); how to solve it is a different story. Why don't you search the forum?


edit: for example, this thread has some of the same search terms in it. Why don't you check it out.
http://www.daniweb.com/forums/thread168656.html