To execute a C language program, a program is needed to handle ROMization for inclusion in the system and to start the user program (main function). This program is called the startup routine.

To execute a user program, a startup routine must be created for that program. The Renesas integrated development environment (IDE) for RX Family provides standard startup routine object files, which carry out the processing required before program execution, and the startup routine source files (assembly source), which the user can adapt to the system.