# Symbol visibility (ivss)

**Symbol visibility** determines whether another object can resolve a symbol by name. A definition exported from `data.s` can satisfy a reference in `main.s`:

```asm
# data.s
.global answer
.section my_data
answer:
    .word 42
.end
```

```asm
# main.s
.extern answer
.section my_code
    ld answer, %r1
    halt
.end
```

Assemble each file separately, then link both objects. The load refers to `answer` without knowing where the data section will be placed. Symbol resolution supplies that location, and execution loads forty-two into `%r1`.

`.global` exports a definition; `.extern` conventionally declares a definition supplied elsewhere. In this implementation both directives mark their symbols with global binding. The label's presence distinguishes a section-defined symbol from an undefined reference.

A plain label is local by default, so its name is not automatically a cross-file interface. Exporting a symbol also does not allocate storage: the label and `.word` supply the definition and data in this example.

Source: [asembler.c](https://github.com/yanevskiv/ivss/blob/main/src/asembler.c).