The following is NOT a complete C program. It is simply intended to provide an idea of how to issue control functions to a device.

This example assumes that DevHandle contains the handle to the device, and that the device recognizes category code hex 83, function code hex 1D and the input parameters and input data area.

 #define INCL_DOSDEVICES   /* Device values */
 #define INCL_DOSERRORS    /* Error values */
 #include <os2.h>
 #include <stdio.h>
 #include <string.h>

 HFILE   DevHandle        = NULLHANDLE;   /* Handle for device */
 ULONG   ulCategory       = 0x83;         /* Device category */
 ULONG   ulFunction       = 0x1D;         /* Device-specific function */
 UCHAR   uchParms[120]    = {0};          /* Input and output for function */
 ULONG   ulParmLen        = 0;            /* Input and output parameter size */
 UCHAR   uchDataArea[200] = {0};          /* Input and output data area */
 ULONG   ulDataLen        = 0;            /* Input and output data size */
 APIRET  rc               = NO_ERROR;     /* Return code */

  strcpy(uchParms,"/X /Y /Z");    /* Input parameters */
  ulParmLen = strlen(uchParms);   /* Length of input parameters */

  strcpy(uchDataArea,"DF=123;NP=BCR;UN=1993;MAX=328");  /* Input data */
  ulDataLen = strlen(uchDataArea);                      /* Length of data  */

  rc = DosDevIOCtl(DevHandle,           /* Handle to device */
                   ulCategory,          /* Category of request */
                   ulFunction,          /* Function being requested */
                   uchParms,            /* Input/Output parameter list */
                   sizeof(uchParms),    /* Maximum output parameter size */
                   &ulParmLen,          /* Input:  size of parameter list */
                                        /* Output: size of parameters returned */
                   uchDataArea,         /* Input/Output data area */
                   sizeof(uchDataArea), /* Maximum output data size */
                   &ulDataLen);         /* Input:  size of input data area */
                                        /* Output: size of data returned   */

  if (rc != NO_ERROR) {
      printf("DosDevIOCtl error: return code = %u\n", rc);
      return 1;
  }