Video

There are 2 video modes, Bitmap and Character. In Bitmap mode, you can write individual pixels to the screen. In character mode, you can write numbers, letters, and symbols to the screen. The characters are overlayed on top of the pixels, so they take priority. In this essence, pixels are “the background” while characters are “the foreground”

Bitmap Mode

In order to write pixels to the screen, it is important to understand the video system of the Astro-8. The screen is 108x108 pixels, meaning there are a total of 11664 memory locations occupied by the screen.

Writing pixels is just like writing to any other part of memory. You simply use whatever command the language provides you with to change that location of memory to a color.

Have a look at the Memory Layout to see where the video memory is mapped.

The colors are stored in 5-bit RGB. Looking at the binary for a single pixel, it would look like this:

RRRRR GGGGG BBBBB

In order to set each of these values, it is often recommended to use bit-shifting. You can also create a function capable of doing this for you. Here is an example using Yabal

inline int get_color(int r, int g, int b) {
    return (r / 8 << 10) + (g / 8 << 5) + (b / 8);
}

This function takes 3 input values, and combines them to create a single word

Characters

The screen supports 18x18 characters, each being 6x6 pixels large