The OCaml system
release 5.5
Documentation and user’s manual
Xavier Leroy,
Damien Doligez, Alain Frisch, Jacques Garrigue,
Didier Rémy, KC Sivaramakrishnan and Jérôme Vouillon
19thJune, 2026
Copyright © 2026 Institut National de Recherche en Informatique et en Automatique
This manual is also available in PDF, plain text, as a bundle of HTML files, and as a bundle of Emacs Info files.

- Contents
- Foreword

# Part I An introduction to OCaml

- Chapter 1 The core language
- Chapter 2 The module system
- Chapter 3 Objects in OCaml
- Chapter 4 Labeled arguments
- Chapter 5 Polymorphic variants
- Chapter 6 Polymorphism and its limitations
- Chapter 7 Generalized algebraic datatypes
- Chapter 8 Advanced examples with classes and modules
- Chapter 9 Parallel programming
- Chapter 10 Memory model: The hard bits

# Part II The OCaml language

- Chapter 11 The OCaml language
- Chapter 12 Language extensions

# Part III The OCaml tools

- Chapter 13 Batch compilation (ocamlc)
- Chapter 14 The toplevel system or REPL (ocaml)
- Chapter 15 The runtime system (ocamlrun)
- Chapter 16 Native-code compilation (ocamlopt)
- Chapter 17 Lexer and parser generators (ocamllex, ocamlyacc)
- Chapter 18 Dependency generator (ocamldep)
- Chapter 19 The documentation generator (ocamldoc)
- Chapter 20 The debugger (ocamldebug)
- Chapter 21 Native debugging (gdb, lldb)
- Chapter 22 Profiling (ocamlprof, perf)
- Chapter 23 Interfacing C with OCaml
- Chapter 24 Optimisation with Flambda
- Chapter 25 Fuzzing with afl-fuzz
- Chapter 26 Runtime tracing with runtime events
- Chapter 27 The “Tail Modulo Constructor” program transformation
- Chapter 28 Runtime detection of data races with ThreadSanitizer

# Part IV The OCaml library

- Chapter 29 The core library
- Chapter 30 The standard library
- Chapter 31 The compiler front-end
- Chapter 32 The unix library: Unix system calls
- Chapter 33 The str library: regular expressions and string processing
- Chapter 34 The runtime_events library
- Chapter 35 The threads library
- Chapter 36 The dynlink library: dynamic loading and linking of object files
- Chapter 37 Recently removed or moved libraries (Graphics, Bigarray, Num, LablTk)

# Part V Indexes

- Index of modules
- Index of module types
- Index of types
- Index of exceptions
- Index of values

- Index of keywords

> This document was translated from LATEX by HEVEA.