# XIO — Examine If Open

Source: https://rungs.dev/docs/ladder-logic/instructions/xio

> XIO (Examine If Open) in rungs.dev passes power along the rung when the referenced bit is 0 — a normally-closed contact.

Passes power along the rung when the referenced bit is `0`. Equivalent to a normally-closed contact.

## Operands [#operands]

| Name      | Type   |
| --------- | ------ |
| `dataBit` | `BOOL` |

## How It Works [#how-it-works]

If `dataBit` is `0`, power passes through. If `1`, power is blocked.

## Example [#example]

```ladder
XIO(Fault)OTE(Ready)
```

`Ready` is energized while `Fault` is `0`.

> **IDEA**
>
> **Practice**
>
> Try `XIO` in the [Lamp Inverted exercise](https://rungs.dev/exercises/lamp-inverted) — light a lamp while a button is released.

## Looking for NOT? [#looking-for-not]

There is no NOT **contact** in Ladder Logic. For inverting a bit on a rung, `XIO` **is** the NOT — it passes power when the bit is off. (Do not confuse it with the Move/Logical [`NOT` block](https://rungs.dev/docs/ladder-logic/instructions/logical), which complements a whole `DINT` word rather than a single bit.)

## Common Mistakes [#common-mistakes]

- Expecting a `NOT` or `!` symbol on a contact — use `XIO` instead.

## Related [#related]

- [XIC](https://rungs.dev/docs/ladder-logic/instructions/xic) — the non-inverted counterpart
- [Bit instructions overview](https://rungs.dev/docs/ladder-logic/instructions/bit-instructions)
- [Logical instructions](https://rungs.dev/docs/ladder-logic/instructions/logical) — the `NOT` block, for inverting a whole `DINT` word