There are a number of different ways to program the VEX microcontroller.
Easy-C and Easy-C Pro is the best drag and drop VEX programming tool out there. It allows beginning roboteers to drag motors, sensors and transmitters to the code stream. There is a pretty decent interactive debugger.
In 2008 RobotC was released. It is positioned between the MPLab compiler and the drag and drop of Easy-C. The advantage of RobotC is the interactive debugger. It's far more detailed and has more features than Easy-C.
RobotC also works with the Lego Mindstorms system.
At the center of Easy-C is a linkable library that can be used to do robot functions. The library makes the MPLabs C compiler easier to develop code with. The WPILibrary has extensive documentation and samples.
You must have EasyC Pro or RobotC for Cortex to program the Cortex.