The C_ dialect provides a set of abstractions for the C programming language. Its reference implementation is a proof of concept that is intended to conform with ISO/IEC 9899:2024 (commonly known as C23), which is the current revision of the C standard. The design is based on a header-only architecture, making it open source by nature; it does not require a separate front-end for C compilers or installation of any additional software. At a high level, the reference implementation is essentially a preprocessing-based transpiler which converts C_ code to C code. Since it is possible to emulate almost the entirety of C_ using C (C23), we do not refer to C_ as a new programming language, but consider it a dialect of C.
C_ was created with an aim to simplify programming, while also making it harder for things to go wrong; the latter is a more ambitious goal, and the extent of its fulfillment largely rests on the programmer. C_ facilitates "abstraction-oriented programming", which blends several concepts from functional programming and object-oriented programming paradigms. Proper use of the right abstractions reduces the chances of bugs.
The best approach to explore a new programming language (or dialect in this case) is to get started by running sample programs. The examples/ directory contains several code snippets that demonstate the usage and workings of C_ features. It contains three sub-directories: .include/, include/, and compile/. The most important task is to make sure that our compiler is able to locate the header files. The sample examples have been tested with gcc (version 14) and clang (version 19), both of which support similar options. For Unix-based systems, if we assume that examples/ is present in the home directory, then the following options can be used:
gcc/clang -xc -std=c23 -iprefix "$HOME"/examples/.include -iwithprefix/ellipsis -iwithprefix/dialect -iwithprefix/library -iprefix "$HOME"/examples/include -iwithprefix/.
If one is using bash shell, then things can be simplified with a command alias placed in ~/.bashrc or ~/.bash_aliases file; here is an example using gcc.
alias cc_="gcc -xc -std=c23 -iprefix '$HOME'/examples/.include -iwithprefix/ellipsis -iwithprefix/dialect -iwithprefix/library -iprefix '$HOME'/examples/include -iwithprefix/.
The file discount.c_ contains an introductory example, which can be compiled as: cc_ lib.c_ discount.c_ (assuming compile/ is the current directory). If things go well, we can run the executable as ./a.out 4 (the program expects number of items as a command-line argument). Executing the script build.sh creates an additional directory named object/ to store object files; the script enables several warnings and optimizations for the compiler (gcc or clang), whose details can be found in the documentation.
Note: Some of the code may not compile with older versions of gcc and clang, due to the use of C23 features whose support was added in recent versions.
The full documentation has been prepared in LaTeX and the file c_.pdf is its generated outcome: it specifies the syntax, constraints, and semantics of various features in C_, without describing the implementation details. Programmers are free to write their own implementation of C_ that conforms to or refines the abstract semantics described in this document.
The intent of documenting C_ in terms of its abstract semantics is two-fold: firstly, readers need not get bogged down to implementation details, which can often be an unnecessary distraction. The second reason is more important: this approach isolates the abstract behavior from any particular concrete implementation, which allows a future scope of providing more efficient translators for C_. Any serious discrepancy between the reference implementation and contents of the documentation is unintentional, and may be considered as a "bug".