 One of these "main lines" is then chosen to drive the whole program, and the others are required to be "inverted" to turn them into subroutines (hence the name "Jackson inversion").This sometimes results in what is called a "clash", requiring the program to be split into multiple programs or coroutines.When using FBP, this inversion process is not required, as every FBP component can be considered a separate "main line".