mirror of
https://github.com/QB64Official/qb64.git
synced 2024-07-16 22:25:14 +00:00
38 lines
2.1 KiB
Markdown
38 lines
2.1 KiB
Markdown
**COMMON SHARED** is used to pass variable values between 2 or more program modules and sub procedures within that module.
|
|
|
|
The multi-modular technique goes back to when QBasic and QuickBASIC had module size constraints. In QB64 it has been implemented so that that older code can still be compiled, though **it is advisable to use single modules for a single project (not counting [$INCLUDE]($INCLUDE) libraries), for ease of sharing and also because the module size constraints no longer exist.**
|
|
|
|
## Syntax
|
|
|
|
> **COMMON** [**SHARED**][/block_name/]variable_list
|
|
|
|
* COMMON statements must be made before any program code execution.
|
|
* The [SHARED](SHARED) statement allows the variable values to also be used in module [SUB](SUB) and [FUNCTION](FUNCTION) procedures.
|
|
* The list of variables(separated by commas) to pass MUST be in the same type order in ALL modules used!
|
|
* [COMMON](COMMON) variable list names(but not variable types) can change between modules.
|
|
* The list can hold any variable type.
|
|
* The list cannot define a variable's value, but can use [AS](AS) to designate the type.
|
|
* Use [DIM](DIM) [SHARED](SHARED) variables when working in a module to pass variable values to SUB procedures.
|
|
* Data files could be used as an alternative to using COMMON SHARED values.
|
|
* In **QB64** COMMON values are sent using files instead of memory presently.
|
|
* **Note: Values assigned to shared variables used as procedure call parameters will not be passed to other procedures! The shared variable value MUST be assigned INSIDE of the [SUB](SUB) or [FUNCTION](FUNCTION) procedure to be passed!**
|
|
|
|
## QBasic/QuickBASIC
|
|
|
|
* Quickbasic 4.5 required you to include BRUN45.EXE when you compile COMMON SHARED values between EXE modules.
|
|
* The COMMON block name designates a certain block of variables that certain program modules may use, the name must be within two forward slashes/ (Ex: /thename/ ). **[Keywords currently not supported by QB64](Keywords-currently-not-supported-by-QB64)**
|
|
|
|
## Example(s)
|
|
|
|
```vb
|
|
|
|
COMMON SHARED x%, y%, user$, speed!, score&
|
|
|
|
```
|
|
|
|
## See Also
|
|
|
|
* [CHAIN](CHAIN), [RUN](RUN)
|
|
* [COMMON](COMMON)
|
|
* [SHARED](SHARED)
|