The article introduces llm.c, a project that aims to train large language models (LLMs) in simple, pure C/CUDA, without relying on PyTorch or cPython. The project provides a reference implementation in C and CUDA, allowing for pretraining and reproducing GPT-2 and GPT-3 models. The goal is to create a fast, efficient, and educational platform for LLM training. The project also includes a library of manually written kernels for various layers, which can be used for educational purposes or to achieve expert-level performance.