Conserving Program Memory; Constants; B-4. Using A Variable Array In Calculations - Campbell CR300 Series Operator's Manual

Appendix B. Introduction to CRBasic Programming
CRBasic Example B-4. Using a Variable Array in Calculations
'This program example demonstrates the use of a variable array to reduce code. In this
'example, two variable arrays are used to convert four temperature measurements from
'degrees C to degrees F.
Public TempC(4)
Public TempF(4)
Dim T
BeginProg
Scan(1,Sec,0,0)
Therm107(TempC(1),1,1,Vx1,0,400,1.0,0)
Therm107(TempC(2),1,2,Vx1,0,400,1.0,0)
Therm107(TempC(3),1,3,Vx2,0,400,1.0,0)
Therm107(TempC(4),1,4,Vx2,0,400,1.0,0)
For T = 1 To 4
TempF(T) = TempC(T) * 1.8 + 32
Next T
NextScan
EndProg
B.2.3 Conserving Program Memory
B.3 Constants
B-6
In this example, a For/Next structure with an incrementing variable is used to
specify which elements of the array will have the logical operation applied to
them. The CRBasic For/Next function will only operate on array elements that
are clearly specified and ignore the rest.
One or more of the following memory-saving techniques can be used on the
rare occasions when a program reaches memory limits:
Declare variables as DIM instead of Public. DIM variables do not
•
require buffer memory for data retrieval.
• Reduce arrays to the minimum size needed. Arrays save memory over
the use of scalars as there is less metadata required per value.
Use variable arrays with aliases instead of individual variables with
•
unique names. Aliases consume less memory than unique variable
names.
• Confine string concatenation to DIM variables.
• Dimension string variables only to the size required.
Constants are discrete packets of CR300 memory that store specific values that
do not vary during program execution. A constant can be declared at the
beginning of a program to assign an alphanumeric name to a value. The
program can then refer to the name rather than the value itself. Using a constant
in place of a value can make the program easier to read and modify, and more
secure against unintended changes. Following is an example of declaring a
constant:
Const CtoF_Mult = 1.8