# Character Position Absolute (HPA)

> Move the cursor to column n of the line it is on.

- **Sequence:** `CSI Pn ``
- **Defaults:** Pn = 1
- **ECMA-48:** [§8.3.57 HPA – Character Position Absolute, p. 45](https://archive.org/details/ecma-48-5th-edition-june-1991/page/n58/mode/1up)
- **VT510:** [HPA—Horizontal Position Absolute](https://vt100.net/docs/vt510-rm/HPA.html)

Move the cursor to column `Pn` of the line it is on, counting from 1. The
line does not change. A `0` is taken as `1`. The VT510 manual says that an
attempt to move past the last position on the line stops at the last
position.

This is [CHA](https://control-codes.page/csi/cha/index.html.md) under another final byte. ECMA-48 defines HPA in
terms of the *data* component and CHA in terms of the *presentation*
component, but a terminal has no separate data component, and for such a
device ECMA-48 reads the one as the other (§6, p. 14). libghostty-vt handles
the two with the same code.

The VT510 manual's one-line summary of HPA, at the top of its page, is a
copying error: it describes asking about free memory for programmable keys.
The description beneath it is the right one.

## Validation

### HPA-1: To a column

Input, one step per line:

```text
\e[2;5H
\e[2`
X
```

Expected screen:

```text
|_____|
|_X___|
```

### HPA-2: To the first column by default

Input, one step per line:

```text
\e[1;4H
\e[`
X
```

Expected screen:

```text
|X____|
```

### HPA-3: Stops at the last column

Input, one step per line:

```text
\e[2;1H
\e[99`
X
```

Expected screen:

```text
|_____|
|____X|
```

---

This is the Markdown version of <https://control-codes.page/csi/hpa/>. On that page every validation case runs live in libghostty-vt, the terminal emulation core of Ghostty, compiled to WebAssembly.

The validation cases are written in the notation described in <https://control-codes.page/notation/index.html.md>.