Structured text, abbreviated as ST or STX, is one of the five languages supported by the IEC 61131-3 standard, designed for programmable logic controllers (PLCs).
[1][2] It is a high level language that is block structured and syntactically resembles Pascal, on which it is based.
[3] All of the languages share IEC61131 Common Elements.
The variables and function calls are defined by the common elements so different languages within the IEC 61131-3 standard can be used in the same program.
Complex statements and nested instructions are supported: Unlike in some other programming languages, there is no fallthrough for the CASE statement: the first matching condition is entered, and after running its statements, the CASE block is left without checking other conditions.