Rockwell Automation 1753-PCS-PAR Using RSLogix Guard PLUS! with GuardPLC Controllers - Manual (Page 94)

Publication 1753-PM001A-EN-P - November 2005
8-8 Create User-Defined Function Blocks
How the Variables Display
Once you declare your variable, the editor displays the variables.
The editor uses these symbols to identify the variables:
Symbol Definition
Used as source
The variable is read from.
Used as sink
The variable is written to.
Used as source and sink
The variable is read from and written to.
Variables used in different types of connections are also identified by this symbol.
Not used as source or sink; but the variable is set in the function block diagram.
Not used
The variable is declared but not set in the function block diagram.