The following is NOT a complete C program. It is simply intended to provide an idea of how a protected-mode OS/2 process can communicate with a virtual device driver (VDD).

This example shows a protected-mode process calling a hypothetical VDD with a request to read a string of bytes from the VDD. Assume that the session identifier of the specified DOS session has been placed into SessionID already and that the sample virtual device driver has registered the name "VDD007" with the operating system.

 #define INCL_DOSMVDM     /* Multiple DOS sessions values */
 #define INCL_DOSERRORS   /* DOS Error values */
 #include <os2.h>
 #include <stdio.h>

 UCHAR   VDDName[10] = "VDD007";    /* Name of VDD */
 HVDD    VDDHandle   = NULLHANDLE;  /* Handle of VDD */
 SGID    SessionID   = 0;        /* Session identifier (should be initialized */
 ULONG   Command     = 3;        /* VDD function code (hypothetical) */
 APIRET  rc          = NO_ERROR;    /* Return code */
 UCHAR   InputBuffer[30]  = "Your command here";  /* Command information    */
 UCHAR   OutputBuffer[30] = "";                   /* Output data (returned) */

    rc = DosOpenVDD(VDDName, &VDDHandle);
    if (rc != NO_ERROR) {
       printf("VDD %s was not found.\n", rc);
       return 1;
    }

    rc = DosRequestVDD(VDDHandle,              /* Handle of VDD */
                       SessionID,              /* Session ID */
                       Command,                /* Command to send to VDD */
                       sizeof(InputBuffer),    /* Length of input */
                       InputBuffer,            /* Input buffer */
                       sizeof(OutputBuffer),   /* Length of output area */
                       OutputBuffer);          /* Output from command */
    if (rc != NO_ERROR) {
        printf("DosRequestVDD error: return code = %u\n", rc);
        return 1;
    }

    rc = DosCloseVDD(VDDHandle);               /* Close the VDD */
    if (rc != NO_ERROR) {
        printf("DosCloseVDD error: return code = %u\n", rc);
        return 1;
    }