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How Does A C Program Work Internally?

The C programming language is one of the most popular programming languages in programming world. Did you know that C++ compilers can be used to develop C apps? You can download C++ IDEs and compilers for free. The IDE and compiler are the first stages of how a C++ or C program works internally. Read on to find out more.

Did you know that a C++ and C program work internally in similar ways?

The C Programming Language was developed in the 1970s and since 1970, there have been many programming languages and have been many changes in C language, like C+, C++, CLANG standards C++99, C++11, C++14, and C++17. C++ programming language includes C language and is powered by Object Oriented Programming features like Classes, Objects and Methods. Still, this venerable language is popular, frequently appearing in the top 3 programming language choices – but if we consider its other variations and its usage on microchips and IoTs it is the most used programming language.

The C++ Compiler and C++ IDE features really evolved from the early and auspicious beginnings of Turbo C, C++ and Borland C++. Today we have a wide array of features supporting a rich and diverse amount of OS platforms running on thousands of types of devices encompassing everything from cell phones, watches, cars to a broad collection of IoT (internet of things) specialized hardware. If we look at the C and C++ programming languages it has more than a %33+ share in programming overall and is still the most popular programming language worldwide. It is really amazing to see the ways in which humanity is benefitting from the advances in technology that have accompanied the evolution of our beloved programming language.

This shared ancestry means that much of how C does things at the internal level is brought forward into C++ programs, at the most very basic low-level. At the code syntax, of course, there are significant differences such as the classes and objects of C++. But when you get down to the bare bones, they are still very definitely siblings.

How Does A C Program Work Internally? A picture of someone holding up a yellow not which says "code" on it

How does a C program work internally when it comes to high-level or low-level syntax

There are two types of programming languages: Interpreted and Non-Interpreted (Compiled). All computers (CPU/GPU) work with machine code that tells the computer what to do. This is the most native and fastest code, but it requires writing many lines for simple things and is hard to generalize for all kinds of machines. A compiler is a computer program that converts one programming language i.e., C/C++ code written with text into executable machine code with a linker.

Such code may not be as fast as assembler code, but the difference in speed is very small because both machine code and compiler-based code in text form are much more compatible with other CPU/GPUs and/or with other Operating Systems when you compile them on a machine. This is one reason why C++ is the fastest and most powerful programming language. Interpreted programming languages run inside executable applications like Java, Python, or Visual Basic. This is why they are slower when executing operations, as they need to use compiled libraries for faster operations. Again, they mostly use C/C++ compilers to build these libraries. Using an interpreted programming language is like being carried by a runner, while a compiled (non-interpreted) programming language is like running itself. This subtle difference turns into a huge gap when you run the same routine for example in face recognition, millions of times a millisecond.

What are the steps in making a C program work internally?

What happens before and after a C program runs? Most simple C or C++ code runs in matter of milliseconds and goes through several entities to give you the output, while their compilation takes longer.

A compiler is a specialized app which can understand and appreciate the processes involved in preprocessing, compiling, linking, loading and running C/C++ programs. A C or C++ application building process involves these stages as illustrated below,

C and C++ IDE and Compiler Stages

1. Making a C program work internally – what is the Coding stage?

The pre stage of the C and C++ programming is where the software developer writes the source code in an IDE or Text editor. The source code is mostly a series of text files with .c or .cpp extensions. There are headers and other files can be included here.

The C files which make up a typical C program may be as follows,

  • file.c C source code which must be preprocessed.
  • file.h C header file (not to be compiled or linked).

A C++ program is made up from the following types of files:

  • file.cpp or file.C C++ source code which must be preprocessed.
  • file.hpp C++ header file
  • file.pch precached header file
  • file.cbproj C++ Builder Project File
  • file.mak C-Make make file
  • file.lib static lib files (which is compiled with the compiler)

2. Making a C program work internally – what is the Preprocessing stage?

Preprocessing is the first stage of compilation, it combines, and processes include files which are added with #include command, conditional compilation instructions and macros.

3. Making a C program work internally – What do we mean by Compilation?

Compilation is the second stage of building a C or C++ program. The IDE’s compiler takes the output of the preprocessor, and the source code, and generates assembler source code.

4. Making a C program work internally – What happens in the Assembly stage?

Assembly stage is the third stage of C compilation. In this stage, compiler takes the assembly source code and produces an assembly listing with offsets. The assembler output is stored in an object file generally with .obj extension. After the source code has been assembled, it will produce an Object files (e.g. .o, .obj) and then linked, producing one (or more) executable files.

5. Making a C program work internally – How does the Linking stage work?

Linking is the final stage of compilation, it combines all compiled object files or libraries and links to a single file, usually this is an executable file. The linker resolves references to external symbols, assigns final addresses to procedures/functions and variables, and revises code and data to reflect new addresses (a process called relocation). Some compilers produce .lnk files after linking, although more commonly linked files are .exe or .a files.

7. Making a C program work internally – What is a Loader?

At the end, the compiler may create many output files and, typically, a single executable file or library. This file can be executed by actions of the operating system (such as when it is a service or daemon), by another app / IDE or by the user launching it. Generally, there are two kinds of executable files, an optimized release version and a debug version which contains extra data and symbols to allow developers to debug the application’s execution at runtime. This executable file may come in several formats such as ELF (Executable and Linking Format) and COFF (Common Object-File Format). For example, ELF is used on Linux systems, while COFF is used on Windows systems. In Windows the executables may have .exe, .com or .dll extensions whereas in UNIX/Linux, the executable or binary file typically doesn’t have extension in or comes with a .out extension. Generally, the GNU C/C++ compiler output is a.out if the output file name is not given – a hangover from the GNU’s days as a compiler for Unix type systems. The compiler may produce a library without an executable, for example it can be a dynamic library like a DLL which needs another program to load it and execute the code it contains.

The COFF is used on Windows systems. Content of these object files have different parts which are called sections. The parts may have executable code, data, dynamic linking information, debugging data, symbol tables, relocation information, comments, code signatures, any embedded resources, string tables, and notes.

All these stages given above are the main processes of the compilation that happen in order regardless of the operating system and the IDE or compiler we use. Generally, these all stages are done by a single compiler command. When we use IDE supported compilers like C++ Builder most of these processes are quite easy even for novice users to develop their applications.

How C Program Works Internally in C++ Builder?

C language is supported by the latest modern C++ IDE’s and compilers. One of the easiest to use and the most professional one is C++ Builder. All the C and C++ IDE and Compiler stages are same in C++ Builder. Moreover, it produces many other outputs to check, debug, watch and pause your application on runtime, plus it comes with deployment tools to support MSIX output for Windows, Android package format for Android and iOS packaging format for the iOS devices.

cbuilder_11_512x5121x-6842885-6973897

C++ Builder is the easiest and fastest C and C++ IDE for building simple or professional applications on the Windows, iOS & Android operating systems. It is also easy for beginners to learn with its wide range of samples, tutorials, help files and LSP support for code. C++ Builder comes with Rapid Application Development Studio, also known as RAD Studio, and C++ Builder is one of the most professional IDE’s that work under RAD Studio. RAD Studio’s C++ Builder version comes with the award-winning VCL framework for high-performance native Windows apps and the powerful FireMonkey (FMX) framework for cross-platform UIs. There is a free C++ Builder Community Edition for students, beginners, and startups.

In 2022, Embarcadero announced the RAD Studio and C++ Builder 11.2. C++ Builder 11.2 contains a number of improvements and quality fixes for C++ developers using C++Builder and RAD Studio 11.1, including performance improvements, display of code completion results, improved navigation, as well as a variety of quality fixes including resolving an issue for users of the classic compiler, issues saving all files in a project, and more. There are also several new features, including handling multiple navigation destinations when Control-clicking on an identifier, delayed indexing to reduce CPU usage, and a third option for LSP Code Insight behavior which indexes all files in all projects. We recommend reading the What’s New in RADS 11.2 in order to tune its behavior for your projects and needs.

What Is C Programming On Windows? A screenshot of the C++ Builder IDE showing the about box and installed libraries.
RAD Studio / C++ Builder Welcome Screen

RAD Studio 11.2 versions are introduced several new features, enhancements, and quality updates in key areas including:   

  • Provision apps for Windows 11
  • C++Builder CodeInsight Update
  • More Powerful Compilers and Debuggers
  • Improved Code Insight!
  • Support for Android API Level 32
  • Compile for macOS M-series (Apple Silicon) processors
  • New & modernized VCL components  
  • Use enhanced remote desktop support to collaborate remotely
  • High-DPI designers for VCL and FireMonkey
  • IDE Support for Markdown, VCL-Based HTML preview
  • IDE Supports high-DPI 4K+ Screens
  • Many Quality Improvements And Bug Fixes


You can download the free C++ Builder Community Edition

Professional developers can use the Professional, Architect or Enterprise versions of C++ Builder.

Please visit https://www.embarcadero.com/products/cbuilder.

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About author

33+ years of coding with more than 30+ programming languages, mostly C++ on Windows, Android, Mac-OS, iOS, Linux and some other operating systems. Dr. Yilmaz Yoru was born in 1974, Eskisehir-Turkey. He graduated from the department of Mechanical Engineering of Eskisehir Osmangazi University in 1997. One year later he started to work in the same university as an assistant. He received his MSc and PhD degrees from the same department of the same university. He has married and he is a father of a son. Some of his interests are Programming, Thermodynamics, Fluid Mechanics and Artificial Intelligence. He also likes the graphical 2D & 3D design and high-end innovations.
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