Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation User Manual
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Appendix K
A-B VBASIC and Visual Basic Tips
K–2
The programmer assumed that this statement would clear the second line of
the display and then print “This is a test”. But, this is not what actually
happens! This is compiled as:
CL2 :
PRINT “This is a test” ;
where CL2 is a local label which is effectively ignored.
The rule should be NEVER have a line which looks like:
< identifier > : < rest of line >
unless you INTEND for
CONSTant Declarations
“CONST name = value” does not quite follow the same rules as variable
assignments in the same position. The major difference is that the type of
‘name’ is determined by the contents of ‘value’. A DEFINT or DEFSNG #,
or $ after the name to set the type explicitly. The trailing symbol is NOT
required when the constant is referenced.
PRINT “text”; :
A problem for Pascal and C programmers is coding: PRINT “text”,
If the statement is a function such as “e = ReadStr%(3,s$)” then the result is
for e to retain its previous value, and for an extra 0 or 1 to follow the printed
text.