MARIE Bitmap Text Renderer

English · 中文

A post-course low-level graphics project demonstrating MARIE assembly, indirect addressing, pointers, subroutines, bitmap fonts, and a memory-mapped 16×16 framebuffer.

This repository is a new implementation inspired by concepts learned in FIT1047. It is not the original assessment submission, and it does not contain the Monash assessment template, specification, or submitted solution.

Core idea

A MARIE-style display exposes 256 memory words (0x0F00–0x0FFF) as a 16×16 framebuffer. A 4×8 bitmap glyph therefore contains 32 pixels. Rendering becomes a pointer-copy problem:

4x8 glyph data
     |
     | LoadI source pointer
     v
accumulator
     |
     | StoreI framebuffer pointer
     v
16x16 memory-mapped display

At the end of each four-pixel glyph row, the destination pointer advances another 12 words to reach the same x-position on the next 16-pixel framebuffer row.

What's included

• assembly/renderer.mas: a clean, standalone MARIE core example that clears the display and paints a glyph using indirect addressing;
• font/glyphs.json: an original 4×8 A–Z bitmap font;
• src/reference_renderer.py: executable Python reference model for six-character, two-row text layout;
• scripts/generate_font_data.py: converts the JSON font into MARIE HEX data words;
• scripts/render_demo.py: renders HELLO as a deterministic ASCII framebuffer;
• unit tests and GitHub Actions CI.

Demo

results/demo.txt contains the 16×16 framebuffer produced by the Python reference model for HELLO. # means foreground and . means background.

#..#.####.#.....
#..#.#....#.....
#..#.#....#.....
####.###..#.....
...

The complete deterministic 16×16 frame is stored in results/demo.txt.

Run the reference model

PYTHONPATH=. python scripts/render_demo.py
PYTHONPATH=. python scripts/generate_font_data.py
python -m unittest discover -s tests -v

Low-level concepts demonstrated

• memory-mapped I/O;
• pointer arithmetic;
• indirect LoadI / StoreI addressing;
• subroutine calls and return-address storage;
• row-major bitmap representation;
• translating 2-D coordinates into linear addresses;
• separation between font data and rendering logic;
• using a high-level reference model to test low-level behaviour.

Origin

This project was rebuilt after learning MARIE and computer-architecture fundamentals in FIT1047 Introduction to Computer Systems, Networks and Security at Monash University. The public repository intentionally avoids publishing assessment materials or a reusable answer to the original task.