Visual patterns in memory?
It looks like a rendered mask for a font (each character in a font (typeface+size+style) is rendered once in-memory, then blitted to the output surface) using 8bpp, which suggests you've got font anti-aliasing enabled.
I'm assuming your project involves a GUI, you might be looking at a shared-memory area that GDI uses for storing rasterized fonts.
If not, then this might just be leftover memory from a previous process or OS component that wasn't zeroed before being used by your application.