Add functions
add_empty(X)
- Point the head and tail of X to the new block
- Reset the empty field of X to zero
- Set the ready flag of the new block low(if X is free_space) and high(if X is queue(i))
add_normal (X)
- Point the tail of X to the new block
- Point the next register of the old tail to the new tail
- Set the ready_flag of the new block low(if X is free_space) and high(if X is queue(i))