Alert view in iphone

To show the alert:

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Do you want to say hello?"
                                                message:@"More info..."
                                               delegate:self
                                      cancelButtonTitle:@"Cancel"
                                      otherButtonTitles:@"Say Hello",nil];
[alert show];
[alert release];

To respond to whatever button was tapped:

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex == 0) {
        NSLog(@"Cancel Tapped.");
    }
    else if (buttonIndex == 1) {
        NSLog(@"OK Tapped. Hello World!");
    }
}

For more information, see the UIAlertView Class Reference and the UIAlertView Delegate Protocol Reference.