The line of code: ```c #define DEFAULT_TRACK_SIZE 16384 ``` is a *C preprocessor directive*...

The line of code:

#define DEFAULT_TRACK_SIZE 16384

is a C preprocessor directive that defines a macro named DEFAULT_TRACK_SIZE with the value 16384.

When the code is compiled, all instances of DEFAULT_TRACK_SIZE in the program will be replaced by the preprocessor with the value 16384 before actual compilation begins. This is often used as a way to define constants in a program for easier management and readability.

For example:

int trackSize = DEFAULT_TRACK_SIZE;

would effectively become:

int trackSize = 16384;

This can be useful for setting named constants that might need to be reused throughout the code or easily changed later.