Cuddly Calculator — Custom Embedded Calculator in C

A fully custom graphing calculator built entirely in C, designed to run on low-resolution embedded displays (128×64 pixels). The project includes a custom graphics engine, a mathematical expression parser, and a desktop LCD simulator for development and testing.

Components

Graphics Library

A pixel-based rendering engine built from scratch, featuring:

• Pixel surface abstraction for framebuffer manipulation
• Software renderer with font rendering, UI elements (scroll text, scroll lists, buttons), and texture support
• Scene system with input handling and update loops
• Math primitives — 2D/3D vectors, 3×3 matrices, and rectangles
• Two display backends: SDL2 (graphical window) and ncurses (terminal)

Math Interpreter

A recursive-descent expression parser that evaluates mathematical expressions with:

• Standard arithmetic operators with correct precedence (+, -, ×, ÷, ^)
• Built-in functions: sin, cos, mod, pow
• Constants: pi
• Variable support (x) for function graphing
• Previous answer reference (ans)

Programs

• Calculator — Expression input with real-time function prediction and result display
• 2D Graph — Plots mathematical functions with adjustable scale and pan controls
• 3D Graph — Three-dimensional function visualization
• Menu — Navigation system between programs

Tools

• LCD Simulator — Runs the calculator UI in a desktop window via SDL2, simulating the target embedded display
• BMP to C — Converts bitmap images into C header files with pixel arrays, used for embedding fonts and icons directly in the binary

Tech Stack

Code is available HERE