ZBasic Language Reference
59
ZBasic Microcontrollers
Sub Main()
Dim i as Byte, j as Byte
i = 44
Test.i = 55
For j = 0 to 1
Dim i as Byte
For i = 1 to 3
Dim i as String
i = "Hello"
Debug.Print i
Debug.Print CStr(Main.i)
Debug.Print CStr(Test.i)
Next i
Next j
End Sub
The first Debug.Print will display the string "Hello" because it refers to the variable i that is defined
in the body of the innermost For loop. The second Debug.Print will display the value 44 because it
refers to the variable i defined at the outermost level of the subroutine using the subroutine name
qualifier. The third Debug.Print will display the value 55 because it refers to the module-level variable
i using the module qualifier. Within the body of the innermost For loop, there is no way to access the
loop index variable because it is hidden by the local definition. There is no qualifier that can be added to
a variable reference to resolve to outer block scope levels except the block formed by the routine
definition itself.
Since ZBasic implements true block scoping, one advantage to using variables defined within compound
statements is that, in addition to the restricted visibility, the stack space used by the variables can be
reused by local variables defined in subsequent compound statements.
Example
If (j > 5) Then
Dim i as Byte
i = 12
Call PutPin(i, zxOutputLow)
Else
Dim s as Single
s = 3.14159
debug.print CStr(s)
End If
For k = 1 to 10
Dim b as Byte
b = GetPin(13)
Debug.print CStr(b)
Next k
In this example, the three variables i, s and b share the same stack space. That works because none of
them are “active” at the same time.
BasicX Compatibility Note
In BasicX mode, block scoping of variables is not supported. It is permitted to define
variables within a compound statement but the effect is the same as if they were
defined at the beginning of the routine.
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