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The X# language knows commands and statements. The difference between these two is:

Statements are defined by the compiler. Examples are the declarations of functions,local variables and control structures such as IF statements and FOR statements

Commands are defined in a header file and are preprocessed by the compiler into function calls. Examples of a Command are the USE command and APPEND BLANK command


Statements are available in almost all dialects, with only a few exceptions.

The available commands are very much dependent on the dialect. For example in the Core dialect no commands are available at all. Most commands have optional parameters and depend on the X# runtime types such as USUAL


This reference lists both the commands that are 'built-in' into the compiler and commands that are defined as default 'User Defined Commands' in STD.UDC.

Some commands are marked with an asterisk as 'deprecated'. They may not be available in future versions of %APP%


Built-in Statements

Commands in header file

Commands in header file

Grouped by category



Concurrency Control



Entity Declaration





Memory Variable


Program Control

Runtime Declaration

Terminal Window

Variable Declaration