Free C++ to C Converter Online

How to use the C++ to C converter?

Follow the steps below to easily convert C++ to C and turn CPP source into C99-compatible code in just a few seconds.

• Add your C++ code: Paste your CPP source into the input box, upload a file, load code from a URL, or click Add Sample Code to try the converter instantly.
• Click Convert to C: Press the Convert to C button. The converter rewrites includes, namespaces, classes, and iostream calls into C99-compatible C directly in your browser.
• Review the C output: Read the generated C code in the output panel and check any TODO comments that mark constructs needing manual review.
• Copy or download: Use the copy button to send the C source to your clipboard, or download the result as a .c file ready for your compiler.
• Iterate if needed: Simplify templates or replace STL containers in your C++ source, then convert again for cleaner C output.

Why use the C++ to C converter?

These benefits make C++ to C converters essential for embedded developers, students, and engineers porting code to legacy systems.

• Embedded Compatibility: When you convert C++ to C, the result runs on tiny microcontrollers and embedded targets that lack a C++ compiler.
• Legacy Toolchain Support: A cpp to C converter helps port code to older toolchains that only support C89 or C99.
• Cross-Language Reuse: Converting CPP to C makes your code callable from other C-based languages without a C++ ABI dependency.
• No Installation Needed: The free C++ to C converter works directly in the browser with no toolchain setup. You can also run the original source in the online C++ compiler before porting it.
• Instant Conversion: Tools quickly convert C++ to C within seconds for typical function-sized snippets.
• Educational Value: Students use a cpp to C converter to learn how C++ features lower to plain C constructs.
• Predictable Output: The C++ to C converter produces consistent, paste-ready C that compiles cleanly with GCC, Clang, or MSVC.
• Free to Use: The converter is completely free with no signup, no credit card, and no usage cap.

Key features of the C++ to C converter

Here are the key features of the C++ to C converter that help you transpile CPP source into C99-compatible code efficiently.

• Include Header Mapping: Replaces C++ headers like <iostream> and <cstring> with their C equivalents during cpp to C conversion.
• Namespace Stripping: Removes using namespace declarations and qualifies symbols where needed for valid C output.
• Class to Struct: Maps simple C++ classes to plain C struct definitions with prefixed function names for methods.
• Iostream to Printf: Converts basic cout and cin lines to printf and scanf with matching format specifiers.
• Memory Allocation Mapping: Maps new and delete to malloc and free where the conversion is safe.
• Access Specifier Removal: Strips public, private, and protected keywords that have no meaning in plain C.
• Automatic Header Management: Adds required C headers such as stdio.h, stdlib.h, and stdbool.h when the output needs them, and removes duplicate includes.
• TODO Markers: The C++ to C converter inserts TODO comments where complex constructs (templates, virtual functions) need manual review.

Use cases of the C++ to C converter

Here are some common ways developers use the C++ to C converter to port code across compilers and platforms.

• Embedded Firmware Porting: Engineers convert CPP utility code into C99 to run on microcontrollers that only ship with a C compiler.
• Legacy Codebase Migration: Teams maintaining old codebases use a cpp to C converter to integrate modern logic with legacy C modules, sometimes alongside the Assembly to C converter for low-level routines.
• Cross-Compiler Compatibility: Developers convert C++ to C to make code build on compilers that lack full C++ support.
• FFI Bindings: Library authors convert C++ APIs to a C interface so other languages can call them via standard FFI tooling.
• Education and Teaching: Educators show students how high-level C++ features lower to plain C constructs, pairing it with the Python to C converter for cross-language comparisons.
• Algorithm Sharing: Algorithm authors publish C++ implementations and ship a C version generated by the cpp to C converter for portability. Prototypes written in Python can first move to C++ with the Python to C++ converter.
• Kernel and Driver Work: Kernel modules and drivers, which prefer plain C, can reuse algorithms originally written in C++.
• Performance Audits: Engineers convert C++ hot loops to C to compare codegen and identify abstractions adding overhead.

Frequently Asked Questions (FAQs)

What is a C++ to C converter?

A C++ to C converter is a tool that transpiles C++ source code into C99-compatible C. It rewrites headers, namespaces, classes, and iostream calls into plain C equivalents so the code can build in environments where only a C compiler is available.

How does the C++ to C converter work?

The converter tokenizes your C++ source in the browser, then rewrites includes, strips using namespace declarations, maps classes to structs with prefixed functions, and converts basic cout and cin lines to printf and scanf. Nothing is uploaded, so the conversion runs entirely on your device.

Is the C++ to C converter free?

Yes. The C++ to C converter is completely free to use with no sign up, no subscription, and no usage cap. It is maintained by TestMu AI as part of its collection of free online developer tools, and the converted C output carries no watermark.

Which C standard does the output target?

The converter targets C99-compatible output, which also compiles cleanly under C11 toolchains. Constructs such as bool receive a stdbool.h include automatically. If you need strict C89, review the generated code for declarations mixed with statements and adjust those few spots by hand.

Does the converter handle C++ classes?

Yes, simple classes are mapped to C struct definitions. Member variables become struct fields, while constructors and methods become free functions prefixed with the class name and taking a self pointer. Inheritance, virtual functions, and operator overloads still need manual restructuring for valid C.

Can it convert iostream to printf and scanf?

Yes. Basic cout chains with string literals, variables, and endl are converted to printf calls with matching format specifiers, and simple cin lines become scanf calls. Heavily chained or formatted output may need manual adjustment after the conversion completes.

Is the converted C code production-ready?

Treat it as a strong starting point rather than a finished port. Common patterns compile close to as-is, but member functions, references, templates, and heavy STL usage are flagged with TODO comments and usually require manual restructuring, review, and testing like any ported code.

Does it support templates and STL containers?

Only partially. Template headers are commented out, simple vector initializations become C arrays or malloc calls, and common string methods map to C library calls like strlen. Advanced templates, operator overloads, and richer STL containers are flagged with TODO comments so you can refactor them by hand.

What is the difference between C++ and C?

C is a procedural systems language with a small core of functions, pointers, and structs. C++ builds on C and adds classes, namespaces, templates, exceptions, and the STL. Converting C++ to C means lowering those higher-level abstractions into plain functions and structs.

Can I download the converted C code?

Yes. After conversion you can copy the C source to your clipboard or click the download button to save it as a .c file. The file is generated locally in your browser and is ready to compile with GCC, Clang, or any standard C compiler.