Appendix B. Introduction to CRBasic Programming
B-4
B.2.1 Declaring Data Types
Variables and data values stored in final memory can be configured with
various data types to optimize program execution and memory usage.
The declaration of variables with the
Public
or
Dim
instruction allows an
optional type descriptor
As
that specifies the data type. The default data type
(declaration without a descriptor) is
IEEE4
floating point, which is equivalent
to the
As Float
declaration. Variable data types are listed in TABLE
shows various data types in use in the declarations and
output sections of a program.
TABLE B-2. Data Types in Variable Memory
Name
Command
Description
Word Size
(Bytes)
Notes
Resolution / Range
Float
As Float
or
As IEEE4
IEEE floating point
4
Data type of all variables unless
declared otherwise.
IEEE Standard 754
±
1.4E–45 to
±
3.4E38
Double
As Double
or
As IEEE8
Double precision
floating point
8
IEEE Standard 754
Use to minimize floating point errors
when doing floating point
calculations or to store measurements
of high-resolution digital sensors.
Suitable for storing numbers larger
than Longs.
±4.94065E-324 to ±1.79769E308
Long
As Long
Signed integer
4
Use to store integer data.
Speed: integer math is faster than
floating point math.
Resolution: 32 bits.
Suitable for storing whole numbers,
counting numbers, and integers in
final-data memory. If storing non-
integers, the fractional portion of the
value is lost.
–2,147,483,648 to +2,147,483,647
Boolean
As Boolean
Signed integer
4
Use to store true or false states, such
as states of flags and control ports. 0
is always false. –1 is always true.
Depending on the application, any
other number may be interpreted as
true or false. See Appendix
.
True
= –
1 or any number ≥ 1
False
= any number ≥ 0 and < 1
String
As String
ASCII string
Minimum: 3
(4 with null
terminator)
Default: 24
Maximum:
limited only
to the size of
available
CR300
memory.
See caution.
1
String size is defined by the CR300
operating system and the CRBasic
program.
When converting from
String
to
Float
, numerics at the beginning of a
string convert, but conversion stops
when a non-numeric is encountered.
If the string begins with a non-
numeric, the
Float
will be
NAN
. If
the string contains multiple numeric
values, the
SplitStr()
instruction can
be used to parse out the numeric
values. Refer to
CRBasic Editor
Help
.
Unless declared otherwise, string size is 24
bytes or characters. String size is allocated
in multiples of four bytes; for example,
String * 25
,
String * 26
,
String * 27
, and
String * 28
allocate 28 bytes (27 usable).
Minimum string size is 4 (3 usable). See
CRBasic Editor Help
for more information.
Maximum length is limited only by
available CR300 memory.
1
CAUTION: When using a very long string in a variable declared
Public
, the operations of datalogger support software will frequently transmit the entire
string over the communication link. If communication bandwidth is limited, or if communications are paid for by the byte, declaring the variable
Dim
may be preferred.
Содержание CR300 series
Страница 2: ......
Страница 6: ......
Страница 68: ...CR300 Series Datalogger 58...
Страница 70: ......
Страница 85: ......