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Convert FJ to C

Can you convert FJ to C?
Verified by Adam B.· reviewed by FE Editorial ·updated Jul 4, 2026
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Is it possible to convert FJ to C?
No - not a direct conversion.

FlipJump is a one-instruction esoteric language and .fj files are its assembly-style source. The only C-related tool, c2fj, goes the other way (C into FlipJump), and there is no tool that reconstructs C from .fj. If you want C, you write it yourself and compile it to FlipJump, not the reverse.

No direct path
Also to C: DLL · SLX · L

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Last verified Sep 2026

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Why convert FJ to C?

People see the c2fj project and assume conversion works both ways to get .c from a .fj file. But FlipJump is a low-level target where the original high-level structure is gone once compiled, so decompiling back to meaningful C is not feasible. The practical route is authoring C and compiling it down to FlipJump.

How to convert FJ to C

c2fj (compile C to FlipJump)

Write your program in .c and use tomhea's c2fj to compile it into FlipJump - this replaces the missing reverse path by working from C in the first place.

Read and rewrite by hand

Open the .fj file in a text editor and manually re-implement its logic in C; there is no automated .fj-to-.c translator.

About these formats

.FJ FlipJump Source Code File

A .fj file is source code written in FlipJump, an esoteric one-instruction programming language whose only operation flips a bit and then jumps to an address. The file is plain text, so any…

Open .FJ details →
.C C Source Code File

A .c file is C source code - plain text that a programmer writes, which a compiler turns into a runnable program. Open it for reading in any text editor (Notepad++, VS Code, Vim). To…

Open .C details →

Quality & what to watch

  • No decompiler exists that produces .c from .fj; the conversion is one-directional (C to FlipJump only).
  • Even a manual rewrite is hard because FlipJump has a single flip-then-jump instruction with none of C's structure.
  • c2fj solves the opposite problem, so it cannot recover C from an existing .fj file.

Frequently asked questions

Can I decompile a .fj file to C?
No. There is no FlipJump-to-C decompiler; the high-level structure is lost during compilation.
What does c2fj do then?
c2fj compiles C source into FlipJump (.fj/.fjm) - the reverse of what you are asking for.
How can I get C code that behaves like a .fj program?
Read the .fj logic and rewrite it in C by hand, or start from C and compile down with c2fj.
Is FlipJump meant to be human-readable?
It is minimal assembly with one instruction, so it is far harder to read than C and does not map cleanly back to it.