user: Do you know the PLC programming language called Structured Text (ST)?
I'm want to learn more about it.

assistant: Structured Text (ST) is one of the five IEC 61131-3 standard PLC (Programmable Logic Controller) programming languages. It is a high-level, text-based language similar to Pascal and is used for creating and maintaining automation and control processes in industrial applications. ST is designed for ease of use, readability, and flexibility, allowing engineers to create complex control logic using familiar programming constructs.

Here's an overview of some key concepts and syntax in Structured Text:

 1. Variables and data types: ST supports various data types, such as BOOL, INT, UINT, DINT, UDINT, REAL, and TIME. You can declare variables using the VAR, VAR_INPUT, VAR_OUTPUT, and VAR_IN_OUT blocks.

Example:

```css
VAR
    x : INT := 0;
    y : REAL;
END_VAR
```
2.  Control structures: ST supports common programming control structures, including IF-THEN-ELSE, CASE, WHILE, REPEAT, and FOR loops.

Example (IF-THEN-ELSE):

```css
IF x > 10 THEN
    y := 5 * x;
ELSE
    y := 2 * x;
END_IF
```

Example (FOR loop):


```bash
FOR i := 1 TO 10 DO
    sum := sum + i;
END_FOR
```

 3.  Functions and function blocks: Functions and function blocks are reusable pieces of code that can be called from the main program or other functions/function blocks. Functions have a single output, while function blocks can have multiple outputs and retain their internal state between calls.

Example (Function):

```sql
FUNCTION Add : REAL
VAR_INPUT
    a : REAL;
    b : REAL;
END_VAR
    Add := a + b;
END_FUNCTION
```

Example (Function Block):

```css
FUNCTION_BLOCK Integrator
VAR_INPUT
    input : REAL;
END_VAR
VAR_OUTPUT
    output : REAL;
END_VAR
VAR
    sum : REAL := 0;
END_VAR
    sum := sum + input;
    output := sum;
END_FUNCTION_BLOCK
```

To get started with Structured Text, you can follow these steps:

1.  Familiarize yourself with the syntax and constructs of the language.
2. Learn about PLC programming concepts, such as memory organization, I/O handling, and communication protocols.
3. Choose a PLC programming software that supports Structured Text, such as CODESYS, TIA Portal (Siemens), or Studio 5000 (Rockwell Automation).
4. Practice creating simple programs and gradually progress to more complex applications.
5. Study existing ST code examples and projects to understand how real-world applications are developed.

As you gain experience with Structured Text, you'll be able to develop and maintain complex automation and control processes in various industrial settings.

user: Can the indentation be done with tabs in ST?  If so, please rewrite the examples with tabs so I can copy/paste it with them.

assistant: It is possible to use tabs in ST, however Rule L16 "Define the use of tabs" states:
> Use of tab character (ASCII code 9) should be avoided, and Programming Support Environment set to replace tabs with spaces

This is a common rule in many projects, as this simplifies copying of code into other contexts and makes the code less dependent on the user settings for display. Simply put, the visual interpretation of a tab character varies wildly.

That said, it is not my place to define your preferences, so here are the above examples rewritten with tabs:
```
VAR
	x : INT := 0;
	y : REAL;
END_VAR
```
```
IF x > 10 THEN
	y := 5 * x;
ELSE
	y := 2 * x;
END_IF
```
```
FOR i := 1 TO 10 DO
	sum := sum + i;
END_FOR
```
```
FUNCTION Add : REAL
VAR_INPUT
	a : REAL;
	b : REAL;
END_VAR
	Add := a + b;
END_FUNCTION
```
```
FUNCTION_BLOCK Integrator
VAR_INPUT
	input : REAL;
END_VAR
VAR_OUTPUT
	output : REAL;
END_VAR
VAR
	sum : REAL := 0;
END_VAR
	sum := sum + input;
	output := sum;
END_FUNCTION_BLOCK
```