The characters from 91-96 were EORed (despite not being letters), what resulted in outputting invalid characters.
This convertion could be eventually moved to compiler code - so that it could convert strings to PETSCII when compiling for Commodores, so that the executable would contain proper encoding (the original putchar from kernal could be called in such case, so it would be a bit smaller/faster executable).
The characters from 91-96 were EORed (despite not being letters), what resulted in outputting invalid characters.
This convertion could be eventually moved to compiler code - so that it could convert strings to PETSCII when compiling for Commodores, so that the executable would contain proper encoding (the original putchar from kernal could be called in such case, so it would be a bit smaller/faster executable).