In this video, you will see how to copy individual chars in STEP 7 to form a STRING variable.The demos is done in STL and the final STRING is validated by comparison .
It is a great example from Siemens forum to learn string manipulation in STL for different Siemens PLCs that are listed.
Original discussion:
https://support.industry.siemens.com/...
How copy chars to STRING in SIEMENS STEP 7 and STRING validation | STL | S7-300 | S7-400 | S7-1500