In the startup of the RL78-S1 core with a small ROM/RAM area, the entire RAM is initialized instead of initializing the stack area or bss attribute areas, from the point of code efficiency. The start address (__RAM_ADDR_START) and end address (RAM_ADDR_END) of RAM are determined by the linker. For __RAM_ADDR_START and __RAM_ADDR_END, see "6.2.2 Symbols generated by option specifications".