Walkthrough: Compile a C program on the command line

The Visual Studio build tools include a C compiler that you can use to create everything from basic console programs to full Windows Desktop applications, mobile apps, and more. Microsoft C/C++ (MSVC) is a C and C++ compiler that, in its latest versions, conforms to some of the latest C language standards, including C11 and C17.

This walkthrough shows how to create a basic, "Hello, World"-style C program by using a text editor, and then compile it on the command line. If you'd rather work in C++ on the command line, see Walkthrough: Compiling a Native C++ Program on the Command Line. If you'd like to try the Visual Studio IDE instead of using the command line, see Walkthrough: Working with Projects and Solutions (C++) or Using the Visual Studio IDE for C++ Desktop Development.

Prerequisites

To complete this walkthrough, you must have installed either Visual Studio or the Build Tools for Visual Studio and the optional Desktop development with C++ workload.

Visual Studio is a powerful integrated development environment that supports a full-featured editor, resource managers, debuggers, and compilers for many languages and platforms. For information on these features and how to download and install Visual Studio, including the free Visual Studio Community edition, see Install Visual Studio.

The Build Tools for Visual Studio version of Visual Studio installs only the command-line toolset, the compilers, tools, and libraries you need to build C and C++ programs. It's perfect for build labs or classroom exercises and installs relatively quickly. To install only the command-line toolset, download Build Tools for Visual Studio from the Visual Studio downloads page and run the installer. In the Visual Studio installer, select the Desktop development with C++ workload (in older versions of Visual Studio, select the C++ build tools workload), and choose Install.

When you've installed the tools, there's another tool you'll use to build a C or C++ program on the command line. MSVC has complex requirements for the command-line environment to find the tools, headers, and libraries it uses. You can't use MSVC in a plain command prompt window without some preparation. You need a developer command prompt window, which is a regular command prompt window that has all the required environment variables set. Fortunately, Visual Studio installs shortcuts for you to launch developer command prompts that have the environment set up for command line builds. Unfortunately, the names of the developer command prompt shortcuts and where they're located are different in almost every version of Visual Studio and on different versions of Windows. Your first walkthrough task is to find the right shortcut to use.

These instructions vary depending on which version of Visual Studio you're using. To see the documentation for your preferred version of Visual Studio, use the Version selector control. It's found at the top of the table of contents on this page.

If you're using a different version of Windows, look in your Start menu or Start page for a Visual Studio tools folder that contains a developer command prompt shortcut. You can also use the Windows search function to search for "developer command prompt" and choose one that matches your installed version of Visual Studio. Use the shortcut to open the command prompt window.

Next, verify that the developer command prompt is set up correctly. In the command prompt window, enter cl (or CL, case doesn't matter for the compiler name, but it does matter for compiler options). The output should look something like this:

C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise>cl
Microsoft (R) C/C++ Optimizing Compiler Version 19.10.25017 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

usage: cl [ option... ] filename... [ /link linkoption... ]

There may be differences in the current directory or version numbers, depending on the version of Visual Studio and any updates installed. If the above output is similar to what you see, then you're ready to build C or C++ programs at the command line.

If you can't find the developer command prompt shortcut, or if you get an error message when you enter cl, then your Visual Studio installation may have a problem. If you're using Visual Studio 2017 or later, try reinstalling the Desktop development with C++ workload in the Visual Studio installer. For details, see Install C++ support in Visual Studio. Or, reinstall the Build Tools from the Visual Studio downloads page. Don't go on to the next section until the cl command works. For more information about installing and troubleshooting Visual Studio, see Install Visual Studio.

Create a C source file and compile it on the command line

1. In the developer command prompt window, enter cd c:\ to change the current working directory to the root of your C: drive. Next, enter md c:\hello to create a directory, and then enter cd c:\hello to change to that directory. This directory will hold your source file and the compiled program.

2. Enter notepad hello.c at the developer command prompt. In the Notepad alert dialog that pops up, choose Yes to create a new hello.c file in your working directory.

3. In Notepad, enter the following lines of code:

   #include <stdio.h>
   
   int main()
   {
       printf("Hello, World! This is a native C program compiled on the command line.\n");
       return 0;
   }
   

4. On the Notepad menu bar, choose File > Save to save hello.c in your working directory.

5. Switch back to the developer command prompt window. Enter dir at the command prompt to list the contents of the c:\hello directory. You should see the source file hello.c in the directory listing, which looks something like:

   C:\hello>dir
    Volume in drive C has no label.
    Volume Serial Number is CC62-6545
   
    Directory of C:\hello
   
   10/02/2017  03:46 PM    <DIR>          .
   10/02/2017  03:46 PM    <DIR>          ..
   10/02/2017  03:36 PM               143 hello.c
                  1 File(s)            143 bytes
                  2 Dir(s)  514,900,566,016 bytes free
   
   

   The dates and other details will differ on your computer. If you don't see your source code file, hello.c, make sure you've changed to the c:\hello directory you created, and in Notepad, make sure that you saved your source file in this directory. Also make sure that you saved the source code with a .c file name extension, not a .txt extension.

6. To compile your program, enter cl hello.c at the developer command prompt.

   You can see the executable program name, hello.exe, in the lines of output information that the compiler displays:

   c:\hello>cl hello.c
   Microsoft (R) C/C++ Optimizing Compiler Version 19.10.25017 for x86
   Copyright (C) Microsoft Corporation.  All rights reserved.
   
   hello.c
   Microsoft (R) Incremental Linker Version 14.10.25017.0
   Copyright (C) Microsoft Corporation.  All rights reserved.
   
   /out:hello.exe
   hello.obj
   

   Note

   If you get an error such as "'cl' is not recognized as an internal or external command, operable program or batch file," error C1034, or error LNK1104, your developer command prompt is not set up correctly. For information on how to fix this issue, go back to the Open a developer command prompt section.

   If you get a different compiler or linker error or warning, review your source code to correct any errors, then save it and run the compiler again. For information about specific errors, use the search box at the top of this page to look for the error number.

7. To run your program, enter hello at the command prompt.

   The program displays this text and then exits:

   Hello, World! This is a native C program compiled on the command line.
   

   Congratulations, you've compiled and run a C program by using the command line.

Next steps

This "Hello, World" example is about as basic as a C program can get. Real world programs have header files and more source files, link in libraries, and do useful work.

You can use the steps in this walkthrough to build your own C code instead of typing the sample code shown. You can also build many C code sample programs that you find elsewhere. To compile a program that has more source code files, enter them all on the command line:

cl file1.c file2.c file3.c

The compiler outputs a program called file1.exe. To change the name to program1.exe, add an /out linker option:

cl file1.c file2.c file3.c /link /out:program1.exe

And to catch more programming mistakes automatically, we recommend you compile by using either the /W3 or /W4 warning level option:

cl /W4 file1.c file2.c file3.c /link /out:program1.exe

The compiler, cl.exe, has many more options you can apply to build, optimize, debug, and analyze your code. For a quick list, enter cl /? at the developer command prompt. You can also compile and link separately and apply linker options in more complex build scenarios. For more information on compiler and linker options and usage, see C/C++ Building Reference.

You can use NMAKE and makefiles, or MSBuild and project files to configure and build more complex projects on the command line. For more information on using these tools, see NMAKE Reference and MSBuild.

The C and C++ languages are similar, but not the same. The Microsoft C/C++ compiler (MSVC) uses a basic rule to determine which language to use when it compiles your code. By default, the MSVC compiler treats all files that end in .c as C source code, and all files that end in .cpp as C++ source code. To force the compiler to treat all files as C no matter the file name extension, use the /TC compiler option.

By default, MSVC is compatible with the ANSI C89 and ISO C99 standards, but not strictly conforming. In most cases, portable C code will compile and run as expected. The compiler provides optional support for the changes in ISO C11/C17. To compile with C11/C17 support, use the compiler flag /std:c11 or /std:c17. C11/C17 support requires Windows SDK 10.0.20201.0 or later. Windows SDK 10.0.22000.0 or later is recommended. You can download the latest SDK from the Windows SDK page. For more information, and instructions on how to install and use this SDK for C development, see Install C11 and C17 support in Visual Studio.

Certain library functions and POSIX function names are deprecated by MSVC. The functions are supported, but the preferred names have changed. For more information, see Security Features in the CRT and Compiler Warning (level 3) C4996.

See also

Walkthrough: Creating a Standard C++ Program (C++)
C Language Reference
Projects and build systems
Compatibility