Supported languages

The languages LCOJ can judge, how to see which ones are actually available on a site, and how administrators add a new one.

⏱ ~5 min read · 👤 Everyone, administrators

When you need this page

• You want to know whether the site judges your language, or which compiler version it uses.
• A language doesn't appear in the language picker when submitting.
• You are an administrator and want to enable more languages on the site.

LCOJ's judge code (luyencode/judge-server, based on DMOJ and VNOJ) ships executors for close to 70 languages. However, the languages you can actually use on a given site are the ones that site's judges report, not the full list below.

Checking available languages

On an LCOJ site (for example, https://luyencode.net), open:

Page	Contents
/runtimes/	Languages supported by at least one online judge, with compiler/interpreter versions
/runtimes/matrix/	Runtime versions per judge
/status/	Online judges and each judge's runtimes

When you submit, the language dropdown only lists languages that meet all three conditions:

1. An online judge has loaded that language's executor (judges self-test every language at startup and drop the ones that fail).
2. The site database has a Language record whose key matches the executor name (for example, CPP17 or PY3). If a judge reports an executor that has no matching record, the language doesn't appear.
3. The problem setter allowed that language for the problem, and a judge has the problem's data.

Languages on a fresh install

During installation, ./scripts/manage.py loaddata language_small (see Installing with Docker) creates these languages:

Key	Display name	Notes
C, C11	C, C11	GCC
CPP03, CPP11, CPP14, CPP17, CPP20	C++03 … C++20	GCC with the matching C++ standard
PAS	Pascal	Free Pascal
PY2, PY3	Python 2, Python 3	CPython
PYPY, PYPY3	PyPy 2, PyPy 3	Faster Python thanks to a JIT
JAVA8, JAVA	Java 8, Java 19	JAVA uses the newest Java on the judge; the display name is set by administrators
KOTLIN	Kotlin
TEXT	TEXT	Submit the output text directly
OUTPUT	Output Only	File upload only: a .zip of outputs (up to 10 MB)
SCRATCH	Scratch	File upload only: an .sb3 file (up to 1 MB)

To add other languages, an administrator adds a record at /admin/judge/language/ whose key matches the executor name (see the table below).

Don't load language_all on top of language_small

The repo also ships a language_all fixture, but its primary keys (ids) overlap with language_small while the contents differ. Loading it on top would overwrite existing languages incorrectly. Only consider language_all instead of language_small on a fresh database.

Real versions live on /runtimes/

Display names such as "Java 19" are just labels stored in the database. The actual compiler/interpreter versions are reported by the judges and shown on /runtimes/ and in the language dropdown when you submit.

All judge executors

The judge ships the executors below, one module each in its dmoj/executors/ directory. An executor only works when the judge image has the matching runtime installed.

Group	Key (language)
C/C++	C, C11, CLANG (Clang), CPP03, CPP11, CPP14, CPP17, CPP20, CLANGX (Clang++), CICPC, CPPICPC (C/C++ with ICPC-style compiler flags), CPPTHEMIS (Themis-style C++)
Pascal	PAS (Free Pascal), PASTHEMIS (Themis-style Pascal)
Python	PY2, PY3, PYPY, PYPY3
JVM	JAVA8, JAVA, KOTLIN, SCALA, GROOVY
.NET (Mono)	MONOCS (C#), MONOFS (F#), MONOVB (Visual Basic)
JavaScript	NODEJS (Node.js), V8JS (V8), COFFEE (CoffeeScript)
Assembly	GAS32, GAS64, GASARM (GNU as), NASM, NASM64, LLC (LLVM IR)
Systems	GO, RUST, D, ZIG, SWIFT, OBJC (Objective-C), DART
Functional and logic	HASK (Haskell), OCAML, SBCL (Common Lisp), SCM (Scheme), RKT (Racket), PRO (Prolog), LEAN4 (Lean 4)
Scripting	RUBY, PERL, PHP, LUA, TCL, BASH, AWK, SED, PIKE
Classic and other	ADA, CBL (COBOL), F95 (Fortran), FORTH, ALGL68 (Algol 68), TUR (Turing), BF (Brain****), ICK (INTERCAL)
Special	TEXT, OUTPUT (output-only), SCRATCH

Notes

• The most common competitive programming languages are C++ (prefer CPP17 or CPP20), Python 3 (try PYPY3 for heavy problems), Java, and Pascal.
• A problem can set time and memory limits per language. The limits that apply are shown on the problem page.
• Rarely used languages may have undiscovered bugs. If you hit a problem with a language, please report it to the judge project.

Next steps

• Submitting and judging: how to pick a language and submit.
• Status codes: what results such as CE, RTE, and IR mean.
• Setting up judges: for operators, running a judge so the site has languages.
• Glossary: terms such as judge, executor, and runtime.