The program makes the terminal use non-canonical input and output by using termios. Then it updates and prints a 2D character array containing the board borders, snake, and food. Before terminating, the program restores canonical mode.

Each part of the snake is a node of a dynamically allocated linked list that contains:

The snake's x and y coordinates
The character that represents it on the board
The part's direction
A pointer to a order node (more on orders below)
A pointer to the next snake part node

An order keeps information on when a snake part should change to what direction. An order is also a node in a dynamically allocated linked list that contains:

The direction that this order eventually tells the snake part to go to
The delay i.e. how many ticks until the snake part has to change direction.
A pointer to the next order

Info

Only tested with the combination of

GCC
Linux
x86 CPU