Continue changing STRING length from int8_t to uint8_t.
This fix segmentation faults caused by overflow when converting from string to numeric types.
IEC 61131-3 Annex F Examples (informative)
This directory contains example code take from:
Annex F of Draft 2nd edition of the IEC 61131-3 standard (1998)
"PROGRAMMABLE CONTROLLERS - PROGRAMMING LANGUAGES"