Internal Variables and Expressions

Internal Variables

In the ComfileHMI, a Internal variable refers to a named location in the ComfileHMI hardware's memory.

If a Internal variable is used without first being declared, it will be implicitly declared and available for use immediately.

All variables are global, so they must be given unique names, and can be used on any screen.
Variables can only store numeric values. Integers, floating point, and even 64-bit integers are supported).
Variables names are case-sensitive and support Unicode, so variable names can be expressed in any language.
Variable names cannot begin with numeric digits; they must begin with a letter or an underscore character. Variables names should not contain spaces.
- A good example for a motor status variable could be Motor1
- 123abc is invalid because it begins with a numeric digit
- Motor Status is invalid because it contains a space

A list of variables in use can be obtained from Comfile Studio's main menu: Project→View Addresses and Variables in Use.

String Variables

String variables were added in a subsequent version of Comfile Studio. They are declared and used with a $ prefix. For example <html>

$a=&quot;hello&quot;

</html>.

Internal Memory

Internal memory is a specific memory region in the ComfileHMI hardware. It is volatile, so it will be erased when the ComfileHMI hardware is powered off.

There are 1024 memory locations (indexed 0~1023) that can be written to and read from. They can store 64-bit integers and double-precision floating point values.

set_mem(index, value) : Writes value to internal memory at index.
mem(index) : Reads the value current stored in internal memory at index.

Multiple values can be stored adjacently in internal memory by passing multiple value arguments to the set_mem function.

set_mem(index, value1, value2, …, valueN)

See the internal memory functions.

Conditional Expressions

Conditional expressions provide the ability to compare variables.

<, <html>

<=

</html>, ==, >=, >, != operators are supported. They are identical to the comparison operators used in the C programming language.
&& and || are boolean AND and boolean OR operators respectively.

(Example)
MotorStatus > 1
Heater1 == 0 ⇐ true if Heater1 is equal to 0
Heater1 != 0 ⇐ true if Heater1 does not equal 0

Mathematical Expressions

+, -, *, /, and % operators are supported for performing math on variables. They are identical to the arithmetic operators used in the C programming language.

(Example)
MotorStatus + 1

Bitwise Expressions

<html>

>>

</html>, <html>

<<

</html>, |, and & operators are supported for bitwise operations. They are identical to the bitwise operators used in the C programming language.

(Example)
<html>

(bits >> 2) & 1

</html>

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Internal Variables and Expressions