ZBasic Language Reference
7
ZBasic Microcontrollers
Chapter 2 - ZBasic Language Elements
The logic of a program is described in the ZBasic language using identifiers, keywords, literal values,
expression operators, statements, etc. These elements are all more fully described in this chapter.
2.1 Identifiers
In ZBasic, as in most computer languages, all constants, variables, subroutines and functions have a
name. Such names are generally referred to as identifiers and each computer language has rules that
specify how an identifier may be formed. In ZBasic an identifier must begin with an alphabetic character
(A-Z, a-z) and may contain zero or more additional characters which may be alphabetic, numeric (0-9) or
an underscore. There is virtually no maximum number of characters that an identifier may contain (in
reality it is limited by the amount of memory available on your computer) but as a practical matter
identifiers seldom exceed 15 to 20 characters. Beyond that they become somewhat cumbersome to type.
As mentioned previously, the alphabetic case of the letters of an identifier is insignificant. The variable
myVar is the considered the same as the variable MyVar.
There is a set of identifiers that are reserved for special purposes and cannot be otherwise used in your
program. Some of the reserved words are data type names, some are used as keywords in ZBasic
statements (If, For, Sub, etc.). Some reserved identifiers have no current use in ZBasic but they are
reserved nonetheless because they are keywords in other Basic dialects and may be incorporated into
ZBasic in the future. If you attempt to use a reserved word in a role other than its predetermined role the
compiler will issue an error message pointing out the unacceptable use. See Appendix A for a complete
list of reserved words.
2.2 Data Types
The table below describes the fundamental data types available in ZBasic. There are a few additional
data types that are used for special purposes that will be described later.
Fundamental Data Types
Data Type Name
Range of Values
Boolean
True, False
Byte
0 to 255
Integer
-32,768 to 32,767
UnsignedInteger
0 to 65,535
Long
-2,147,483,648 to 2,147,483,647
UnsignedLong
0 to 4,294,967,295
Single
approximately ±1.4e-45 to ±3.4e+38 and 0.0
String
0 to 255 characters
The special type DataAddress is a synonym for the type needed to hold a RAM address. On AVR-
based devices it is the same as UnsignedInteger but on larger devices it is the same as
UnsignedLong.
It is important to note that some mathematical operations on floating point values (type Single) result in
certain special values that indicate an exceptional result. Among these special values are ones that
represent positive infinity, negative infinity and a general category referred to as “not a number”, called
NaN. The System Library function SngClass() returns a value indicating the class to which a floating
point value belongs. See the ZBasic System Library Reference Manual for more information on the
SngClass() function.
In addition to the fundamental data types enumerated in the table above, ZBasic supports several
additional special-purpose types. There are two additional integral-value types that are collectively
referred to as sub-byte types – Bit and Nibble. These are useful for reducing the amount of space
 |
 |
 |