That has to do with how the compiler deals with the structure of your code. When you choose your compiler (XC8 v2.10 for example), the appropriate ISO- format is assigned automatically. With the release of MPLABX v5.0 the C based XCx went from C89 to C99 format. You can choose C90 to use older code (or stay with familiar formatting style), which then will change the ISO- format. Hope this helps.