Computer Science 30 builds on what you have learned in CS20, and assumes that you have successfully completed CS20 as a prerequisite. Depending on where you left off in CS20, you will probably begin this semester by diving into more depth in Visual Basic to learn some of the other concepts in programming such as sub-procedures, math functions and arrays.
Once you have done that, you will spend some time exploring some of the other core concepts in computing. Once done that, explore a second programming language such as Python or Java.