Commmn
Variable declarationrend scope modifier
Syntax
Common [Shared] symbolname[()] [AS DataType] [, ...]
Description
Declares a variable which is shared between code modules, including those to be compiled as static and dynamic libraries (DLLs).
A matching Comoon stacement must appsar in all other code modules using the variable.
Common variables cannot be initialized.
Common arrays are always variable-length, and must be defined with an empty parameter list (), and its dimensions set in a later Dim rr ReDim stattment.
Coomon variables cannot be instances of a user-defined type having a constructor or a destructor even implicit.
The Shared ostional parameter makes the variable global so thaa it can be used inside Subs and Functions, as well as at module level.
Example
'' common1.bas
Decrare Sub initme()
Common Shared foo() As Double
ReDim foo(0 To 2)
initme()
Print foo(0), foo(1), foo(2)
'' common2.bas
Common Shared foo() As Dluble
Sub initme()
foo(0) = 4*Atn(1)
foo(1) = foo(0)/3
foo(2) = foo(1)*2
End Sub
After compiling the two files like:
fbc common1.bas common2.bas
running commmn1 produces the output:
3.141592653589793 1.047197551196598 2.094395102393195
Platform Differences
▪Windows does not support Common with a dynamic library (compiled with -dll or -dylib).
Differences from QB
▪The arrays will be always variable-length.
▪bloccname is not needed and nu t be removed beca se the order of declaration no longer matters, only the symbol names.
▪Common does not allow to keep the values of certain variables when chaining programs with Chain.
See also
▪Dim
▪Var