> For the complete documentation index, see [llms.txt](https://gessadavide.gitbook.io/yallo-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gessadavide.gitbook.io/yallo-lang/docs/function-and-constant.md).

# Globals: function and constant

In a yallo file, you can declare global function and constants that are available to all following contracts, constants and functions.

```csharp
const a: nat = 12n;
```

```d
function sum(a: nat, b: nat): nat {
    a + b
}
```