To open a file for basic I/O operations, set the lpmmioinfo parameter of the mmioOpen function to NULL. The following example opens a file named "C:\SAMPLES\SAMPLE1.TXT" for reading, and checks the return value for error.
HMMIO hFile;
if ((hFile = mmioOpen("C:\\SAMPLES\\SAMPLE1.TXT", NULL,
MMIO_READ)) != NULL)
// File opened successfully.
else
// File cannot be opened.
Use the dwFlags parameter of mmioOpen to specify flags for opening a file.