This example allocates named shared memory as Read/Write, and commits it during allocation. It also writes to it, and show how other processes can access it.

#define INCL_DOSMEMMGR   /* Include DOS Memory Management APIs */
#define INCL_DOSERRORS   /* DOS error values                   */
#include <os2.h>
#include <stdio.h>
#include <string.h>

int main (VOID)
{
   PVOID  pvShrObject = NULL;      /* Pointer to shared memory object      */
   PSZ    pszMemName  = "\\SHAREMEM\\MYTOOL\\APPLICAT.DAT"; /* Object name */
   PVOID  pvAltObject = NULL;      /* Alternate pointer to shared memory   */
   APIRET rc          = NO_ERROR;  /* Return code                          */
   ULONG  ulObjSize   = 1024;   /* Size (system rounds to 4096 - page bdy) */

   rc = DosAllocSharedMem(&pvShrObject,   /* Pointer to object pointer     */
                          pszMemName,     /* Name for shared memory        */
                          ulObjSize,      /* Desired size of object        */
                          PAG_COMMIT |    /* Commit memory                 */
                          PAG_WRITE );    /* Allocate memory as read/write */
   if (rc != NO_ERROR) {
      printf("DosAllocSharedMem error:  return code = %u\n",rc);
      return 1;
   }

   strcpy(pvShrObject, "Write your shared application data here.");

      /* Get the address of the shared memory and reference it that way.
         (Done for illustrative purposes only, this is how another process
         would go about accessing the named shared memory.)            */

   rc = DosGetNamedSharedMem(&pvAltObject,  /* Pointer to pointer of object */
                             pszMemName,    /* Name of shared memory        */
                             PAG_READ);     /* Want read-only access        */
   if (rc != NO_ERROR) {
      printf("DosGetNamedSharedMem error:  return code = %u\n",rc);
      return 1;
   }

   printf("Shared data read was \"%s\"\n",pvAltObject);

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

   return NO_ERROR;
}