Create a Framebuffer and Write a PPM Image

Framebuffers Store Raw Pixel Data

A framebuffer is a region of memory that stores pixel color values. Before GPUs existed, all rendering wrote colors directly into a framebuffer in system RAM. The concept remains central: your monitor displays whatever sits in the framebuffer.

Each pixel typically stores red, green, and blue as 8-bit channels (24 bits total). Some formats add an alpha channel for transparency. Every shader, texture upload, and swapchain present ultimately resolves to reading and writing these bytes.

The PPM Image Format

PPM (Portable Pixmap) is one of the simplest image formats. It stores pixels as plain text, ideal for learning and debugging:

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• P3: ASCII format (P6 is binary)
• Header: width, height, max color value (usually 255)
• Body: three integers per pixel (R G B)

For example, an 8x8 gradient from black at top-left to yellow at bottom-right uses red = (x * 255) / 7 and green = (y * 255) / 7.

For This Exercise

You will create an 8x8 RGB framebuffer, fill it with a red-green gradient, and print a valid PPM header plus pixel data to stdout. This task also asks for an ASCII preview using # and . characters. Our sandbox has no display, so stdout replaces writing a file. The row-major layout you build here is the same abstraction behind Linux /dev/fb0 and every software renderer in this subtrack.