I purchased Training For Xcode from the Apple App store. It appears the code you provide for Read and Write Files does not work with Xcode 7. There are no errors displayed when run but the code is simply ignored during runtime. For one thing there is no Build/Debug directory in Xcode 7. My code follows. The global variables code discussion works fine. Also, I created my text file in every possible location and every attempt returned the null file condition. Can you tell me what has changed in Xcode 7 to make it possible for your description to work properly for reading and writing files? Because your Xcode training course does not appear as a category I chose a similar topic.

    int main(int argc, char *argv[]){
    
// NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
// Define global variables
    gCd = 1.289;
    
// Print a global variables (test)
// NSLog(@"%F", gCd);
    
    NSString *string = @"I like bacon and ham";
    NSLog(@"%@", string);
    
// Read data from file
    NSFileHandle *fin, *fout;
    NSData *buffer; // buffer holds data during read
    
// Open data file for reading and writing
    fin = [NSFileHandle fileHandleForReadingAtPath:@"Data_File"];
    
    [[NSFileManager defaultManager]createFileAtPath:@"Data_File_New" contents:nil attributes:nil];
    fout = [NSFileHandle fileHandleForWritingAtPath:@"Data_File_New"];
    
// truncate file, delete old file contents
    [fout truncateFileAtOffset:0];

// Open data file and transfer it to buffer
    buffer = [fin readDataToEndOfFile];
    
// Copy data from buffer to variables
    [fout writeData: buffer];
    NSLog(@"%@", fout);

// Close input and output files
    [fin closeFile];
    [fout closeFile];
    
// [pool drain];
    return NSApplicationMain(argc, (const char **) argv);

}

Thank you.
John Cipolla