> For the complete documentation index, see [llms.txt](https://guide.cronuszen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guide.cronuszen.com/gpcscripting/gpc-script-guide/learn-gpc/source-layout-and-global-namespace.md).

# Source layout and global namespace

A Live GPC file can contain these top-level forms:

* `define`
* `enum`
* `data(...)`
* typed `const` arrays, strings, images, and adaptive-trigger data
* `remap` and `unmap`
* global `int` variables and runtime arrays
* optional `init` section or sections
* one or more `main` sections
* `combo` / `fcombo` declarations
* user-created `function` declarations

Zen Studio Live accepts multiple `init` and `main` sections. The compiler merges all `init` sections into the one-time initialization phase and all `main` sections into the repeating main phase. Keeping one of each is normally clearer, but split sections in generated or assembled source are valid.

***

### Name spaces

GPC does not place every declared name in one namespace:

| Namespace/scope | Names in it                                                                   |
| --------------- | ----------------------------------------------------------------------------- |
| Data symbols    | Runtime variables and arrays, definitions, enum members, and const-data names |
| Functions       | User-created function names                                                   |
| Combos          | `combo` and `fcombo` names                                                    |
| Function-local  | The parameters declared by that function                                      |

Names must be unique within the namespace that owns them. A variable cannot reuse a definition, enum-member, or const-data name, but function names, combo names, and function parameters are resolved separately from that data-symbol namespace.

Language keywords and built-in **constants** are reserved. Declaring `main`, `if`, or a constant such as `PS5_CROSS` as your own name is a hard error.

Built-in **function** names are not reserved in the data-symbol namespace — `int set_val;` and `define set_val = 5;` both compile. What the compiler does reject is naming a *user-created function* after a built-in; that is reported as `GPC4001`.

{% hint style="warning" %}
Reusing a built-in function name for a variable or definition is legal, but strongly discouraged. Every compiler message about that name becomes ambiguous to read, and anyone maintaining the script later has to work out which `set_val` is meant.
{% endhint %}

***

Names are case-sensitive and follow this shape:

```
[A-Za-z_][A-Za-z0-9_]*
```

Prefer descriptive uppercase names for compile-time constants and lowercase snake case for runtime variables/functions. Even where separate namespaces technically allow the same spelling, distinct names make searches and compiler messages easier to understand.


---

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