Use Build Main File to compile and link all of the changed modules of a multi-module program. The Build Main File command compiles and links all out-of-date files, except missing .QPU files, and creates a single executable file. A file is out of date if it has been edited since it was last compiled, or if it has been compiled since the main file was last built. The main file is always recompiled. Use the Go command in the Run menu to run the program after it is built.