Linux audio device driver problems

Linux audio device driver-Linux general technology-Linux programming and kernel information. For more information, see the following section. # Include
# Include
# Include
# Include
# Include
# Include
# Include
# Include

# Define BUF_LENGTH 2000
# Define CHANNELS 0/* 0 -- single channel; 2 -- double channel */
# Define SAMPLE_RATE 8000

Int set_fmt (int audio_fd, int bits, int rate, int channel)
{
Int status =-1;

If (-1 = ioctl (audio_fd, SNDCTL_DSP_SAMPLESIZE, & bits ))
{
Perror ("ioctl SNDCTL_DSP_SAMPLESIZE ");
Exit (1 );
}

If (-1 = ioctl (audio_fd, SNDCTL_DSP_SPEED, & rate ))
{
Perror ("ioctl SNDCTL_DSP_SPEED ");
Exit (1 );
}

If (-1 = ioctl (audio_fd, SNDCTL_DSP_CHANNELS, & channel ))
{
Perror ("ioctl SNDCTL_DSP_CHANNELS ");
Exit (1 );
}

Return (0 );
}

Main ()
{
Int audio_fd = 0;
Int bytes = 0;
Int I = 0;
Char buf [BUF_LENGTH];


Audio_fd = open ("/dev/dsp", O_RDWR );
If (audio_fd <0)
{
Perror ("open/dev/dsp ");
Exit (1 );
}

If (-1 = (set_fmt (audio_fd, AFMT_U8, SAMPLE_RATE, CHANNELS )))
{
Perror ("set_fmt ");
Exit (1 );
}

For (I = 0; I <5000; I ++)
{
If (-1 = (bytes = read (audio_fd, buf, BUF_LENGTH )))
{
Perror ("read ");
Exit (1 );
}
If (-1 = write (audio_fd, buf, bytes ))
{
Perror ("write ");
Exit (1 );
}

}

Printf ("It'll be closed \ n ");
Close (audio_fd );
}
It cannot be used after compilation. There is no error message, but no sound. Why ??