Explain free space allocation?

Free space allocation is defined as, when system keeps tracks of the free space blocks for allocating space in files, when they are created and also we can reuse the free space released after deleting the files. The system can maintain a free space list that keeps track of the space blocks which are not allocated to files and directories. Whenever we want to delete a file then the free memory space is added to the free space list during the allocation

The free space list can be implement as:

Bitmap or Bit vector Linked List