Microsoft has literal teams with budgets of several millions USD just for the file open/save in Office which is written in C++.
According to wikipedia:
https://en.wikipedia.org/wiki/Universal_Coded_Character_Set
> The UCS has over 1.1 million possible code points available for use/allocation, but only the first 65,536, which is the Basic Multilingual Plane (BMP), had entered into common use before 2000. This situation began changing when the People's Republic of China (PRC) ruled in 2006 that all software sold in its jurisdiction would have to support GB 18030. This required software intended for sale in the PRC to move beyond the BMP.