# How to Build a Text Editor from Scratch Using Build Your Own X

> Build a text editor from scratch with the Build Your Own X repository. Follow step-by-step guides for text buffering cursor management and terminal rendering in C and Rust.

- Repository: [CodeCrafters/build-your-own-x](https://github.com/codecrafters-io/build-your-own-x)
- Tags: tutorial
- Published: 2026-02-23

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**You can build a text editor from scratch by following the curated tutorials in the codecrafters-io/build-your-own-x repository, which provide step-by-step guides for implementing core components including the text buffer, cursor management, and terminal rendering in languages like C and Rust.**

The codecrafters-io/build-your-own-x repository contains a comprehensive collection of do-it-yourself programming tutorials. If you want to build a text editor from scratch, the repository links to language-specific guides that walk you through creating a functional terminal-based editor from the ground up, covering everything from raw terminal input to file persistence.

## Core Architecture of a Text Editor

All text editor tutorials in the repository share a common architectural pattern. Understanding these five core components provides a reusable mental model that applies to any implementation language.

### The Buffer

The **buffer** holds the file's contents in memory and supports insert and delete operations. According to the source analysis, typical implementations use a dynamic array of strings in C, a `Vec<String>` in Rust, or a mutable list in Python to store individual lines.

### The Cursor

The **cursor** tracks the current row and column position, updating on user input. This is typically implemented as a simple `(row, col)` struct that responds to arrow-key events.

### The Renderer

The **renderer** draws the buffer to the terminal and refreshes the display on changes. Implementations vary by language: C tutorials use direct ANSI escape code writes, while Rust tutorials leverage the `crossterm` library for terminal handling.

### Input Handling

The **input handler** reads keystrokes and maps them to editor commands such as insert, delete, and navigation. This requires putting the terminal into raw mode using `termios` in C, `crossterm` in Rust, or `tty` in Python.

### File I/O

**File I/O** handles loading files into the buffer on startup and writing changes back on save. Standard `open/read/write` system calls manage line endings and error handling.

## Step-by-Step Implementation Guide

To build a text editor from scratch using the Build Your Own X guides, follow this progression:

1. **Select a language** - The [`README.md`](https://github.com/codecrafters-io/build-your-own-x/blob/main/README.md) lists tutorials for C (Kilo) and Rust (Hecto), among others. Choose based on your comfort level.
2. **Initialize your project** - Create a new repository with `git init`, `cargo init`, or a `Makefile`.
3. **Implement the buffer** - Start with a resizable in-memory representation using dynamic arrays or vectors.
4. **Add cursor logic** - Store row and column state and update it based on arrow-key events.
5. **Build the renderer** - Write the buffer to the terminal, handling scrolling and status bar display.
6. **Hook up input** - Configure raw mode terminal input and map keys to editor actions.
7. **Add persistence** - Implement write (`:w`) and quit (`:q`) commands using standard file I/O.
8. **Iterate and extend** - Add syntax highlighting, multiple buffers, or GUI front-ends.

## Code Example: Minimal Buffer Implementation in C

The "Kilo" tutorial linked in the repository provides a complete C implementation. Below is a condensed example demonstrating the buffer initialization and file loading logic as implemented in the guide.

```c
/* buffer.c – core text buffer */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    char **lines;      // array of string lines
    size_t line_count;
    size_t capacity;
} Buffer;

/* Allocate an empty buffer */
Buffer *buffer_new(void) {
    Buffer *b = malloc(sizeof(Buffer));
    b->lines = NULL;
    b->line_count = 0;
    b->capacity = 0;
    return b;
}

/* Append a line, growing the array as needed */
void buffer_append_line(Buffer *b, const char *line) {
    if (b->line_count == b->capacity) {
        b->capacity = b->capacity ? b->capacity * 2 : 8;
        b->lines = realloc(b->lines, b->capacity * sizeof(char *));
    }
    b->lines[b->line_count++] = strdup(line);
}

/* Load a file into the buffer, splitting on '\n' */
void buffer_load_file(Buffer *b, const char *filename) {
    FILE *fp = fopen(filename, "r");
    if (!fp) return;               // error handling omitted for brevity
    char *line = NULL;
    size_t len = 0;
    while (getline(&line, &len, fp) != -1) {
        buffer_append_line(b, line);
    }
    free(line);
    fclose(fp);
}

/* Insert a character at a given row/col */
void buffer_insert(Buffer *b, size_t row, size_t col, char c) {
    if (row >= b->line_count) return;
    char *old = b->lines[row];
    size_t old_len = strlen(old);
    char *new = malloc(old_len + 2);   // +1 for new char, +1 for '\0'
    memcpy(new, old, col);
    new[col] = c;
    memcpy(new + col + 1, old + col, old_len - col + 1);
    free(old);
    b->lines[row] = new;
}

```

This scaffold provides the foundation for the cursor handling, screen drawing, and raw-mode input covered in the full tutorial.

## Available Tutorials in Build Your Own X

The [`README.md`](https://github.com/codecrafters-io/build-your-own-x/blob/main/README.md) file in the codecrafters-io/build-your-own-x repository contains direct links to complete editor implementations:

- **C – "Kilo"**: A minimal editor using only the standard library and raw terminal control via `termios`. This tutorial covers all five architectural components using ANSI escape codes for rendering.
- **Rust – "Hecto"**: A modern, type-safe implementation featuring clean modular design. This guide leverages the `crossterm` crate for cross-platform terminal handling.

## Summary

- **Build Your Own X** provides curated, language-specific tutorials for building text editors from scratch.
- All implementations share five core components: a **buffer** for text storage, a **cursor** for position tracking, a **renderer** for display output, an **input handler** for keystrokes, and **file I/O** for persistence.
- The **Kilo** (C) and **Hecto** (Rust) tutorials offer complete step-by-step guides ranging from dynamic memory allocation to raw terminal mode configuration.
- Starting with the buffer implementation provides the foundation for adding cursor logic, rendering, and input handling.

## Frequently Asked Questions

### What programming languages are supported for building a text editor in Build Your Own X?

The repository primarily features tutorials for **C** and **Rust**. The C tutorial ("Kilo") uses standard library functions and `termios` for terminal control, while the Rust tutorial ("Hecto") utilizes modern crates like `crossterm` for cross-platform compatibility.

### Do I need prior operating systems knowledge to build a text editor from scratch?

Basic familiarity with terminal concepts helps but is not required. The tutorials explain how to use `termios` in C or terminal libraries in Rust to handle raw mode input. You should understand pointers (for C) or ownership (for Rust) to manage the dynamic text buffer effectively.

### How does the text buffer handle large files efficiently?

The buffer implementation uses dynamically expanding arrays. In the C example, `buffer_append_line` doubles the capacity (`b->capacity * 2`) when the array fills, ensuring amortized O(1) insertion time. Lines are stored as separate strings, allowing efficient insertion and deletion at specific row and column positions.

### Can I extend these terminal editors into GUI applications?

Yes. The architectural principles—buffer management, cursor positioning, and file I/O—remain identical. You would replace the terminal renderer with a GUI framework (like GTK, Qt, or a web-based renderer) while keeping the core data structures intact. The Build Your Own X tutorials provide the foundational logic that ports to any UI framework.