---
title: "tty.h"
summary: "A virtual text output device"
---

The TTY is a virtual device, that acts as a text IO layer.
It prints keyboard input and process output to the screen.
The keyboard input can be directed to a processes stdin and the processes stdout can be printed to the screen.

Schematic:
```
+-------------------+
| Graphics Renderer |
+-------------------+
            ^  ^
            |  |  +----------+      +-----------------+
            |  |  | TTY      |      | Process (shell) |
            |  |  |          |      |                 |
            |  |--|-[Input]--|-<----|-[stdout]        |
            |     |          |      |                 |
-[Keyboard]----->-|-[Output]-|->----| [stdin]         |
                  +----------+      +-----------------+

```

# `tty_T` - struct
| Name            | Type               | Description                                                                                       |
|-----------------|--------------------|---------------------------------------------------------------------------------------------------|
| graphics_buffer | graphics_buffer_T* | The graphics buffer where all output will be rendered to.                                         |
| output          | pipe_T*            | Points to the linked processes stdin pipe.                                                        |
| input           | pipe_T             | This pipes content will be rendered to the screen. The linked processes stdout should point here. |
| cursor          | position_T         | The cursors position.                                                                             |
| color           | color_argb_T       | The current drawing color.                                                                        |

# `tty_init()` - function (void)
Initializes `g_tty`.

# `tty_update()` - function (void)
Renders the text from the ttys _input pipe_ onto the screen.
This will be automatically called when writing into the ttys _input pipe_.

# `tty_write(string)` - function (uint32_t)
Renders the text from **_string_** onto the screen.
This also writes **_string_** into the ttys _output pipe_.

# `g_tty` - global variable
This is the systems TTY.
Currently, there is no support planned for multiple ttys.