Xylem System 5000 BASIC Manual - Manual (Page 11)

9
Basic Features and Fundamentals
In order to provide greater flexibility and reusability of Basic Programs on the System 5000™ ,
an advanced subset of commands, known as Symbols, are available. These Symbols allow
program parameters to be modified and defined on a Task by Task basis through the touch screen
interface. A single program could potentially be used for multiple purposes with the use of these
Symbols. Symbols begin with an apostrophe(‘), causing their declaration to appear as a
comment, are case-sensitive (the declaration must be uppercase), and end with a colon(:). The
Symbol’s parameters are then specified after the colon.
The following Symbols are available:
‘NAME:
‘DESC:
‘GROUP:
‘IO:
‘VAR:
The ‘VAR: Symbol can be specified many times throughout the program and defines variables
that can be seen and modified through the touch screen interface of the System 5000™. The
remaining Symbols (‘NAME:, ‘DESC:, ‘GROUP:, and ‘IO:) should be specified only once in a
program and provide information about the program itself. All Symbols are optional and are not
required for a program to run properly. An example program can best illustrate their individual
purposes and syntax:
Filename: blink.bas
‘NAME: Blink Digital LED
‘DESC: An LED attached to ground and Digital Port 3
‘GROUP: None
‘IO: Output
‘VAR: blink_delay, 2.5
‘VAR: msg$, “Program Done”
‘VAR: time_skip$, “00:00:00”, STATIC
IF (time_skip$ != DATETIME(ALARM$)) THEN
SETVALUE DIGITAL3, 1
SLEEP blink_delay
SETVALUE DIGITAL3, 0
ENDIF
PRINT msg$
Advanced Programming with Symbols
Beginning with the ‘NAME: Symbol, if it is specified, the string following is used as the I/O
Name seen through the Task Input and Output selection screens. If no ‘NAME: Symbol is found,
the program’s filename is used (e.g. blink.bas). The Name of a program can be modified through
the Basic Management screen after the program has been installed.
The ‘DESC: Symbol provides a simple description that is viewable via Basic Management and
can be helpful to explain the purpose of a program.