Rockwell Automation's Structured Text language for the Logix 5000 series is an implementation of the IEC 1131-3 Structured Text language.
It looks a little like BASIC, I suppose, but it's syntax is based on Pascal, so that's the old-school language it is most similar to.
A good reference manual for the syntax of the ST language in RSLogix 5000 is the Structured Text Programming Manual, Publication 1756-PM007.
You can download it from the literature.rockwellautomation.com website at no charge.