Creating a Simple Dynamic-Link Library

The following example is the source code needed to create a simple DLL, Myputs.dll. It defines a simple string-printing function called myPuts. The Myputs DLL does not define an entry-point function, because it is linked with the C run-time library and has no initialization or cleanup functions of its own to perform.

To build the DLL, follow the directions in the documentation included with your development tools.

For an example that uses myPuts, see Using Load-Time Dynamic Linking or Using Run-Time Dynamic Linking.

// The myPuts function writes a null-terminated string to
// the standard output device.
// The export mechanism used here is the __declspec(export)
// method supported by Microsoft Visual Studio, but any
// other export method supported by your development
// environment may be substituted.
#include <windows.h>
#define EOF (-1)
#ifdef __cplusplus    // If used by C++ code, 
extern "C" {          // we need to export the C interface
__declspec(dllexport) int __cdecl myPuts(LPCWSTR lpszMsg)
    DWORD cchWritten;
    HANDLE hConout;
    BOOL fRet;
    // Get a handle to the console output device.

    hConout = CreateFileW(L"CONOUT$",

    if (INVALID_HANDLE_VALUE == hConout)
        return EOF;
    // Write a null-terminated string to the console output device.
    while (*lpszMsg != L'\0')
        fRet = WriteConsole(hConout, lpszMsg, 1, &cchWritten, NULL);
        if( (FALSE == fRet) || (1 != cchWritten) )
            return EOF;
    return 1;
#ifdef __cplusplus