operating-systems file-management
Definition
Free Space Management
Free space management refers to the techniques used by the OS to track and allocate unassigned blocks on a secondary storage device.
Methods
Bit Table (Bitmap)
A vector where each bit represents one disk block:
0: Block is free1: Block is allocatedBenefit: Small space overhead, fast contiguous free block search.
Chained Free Portions
A linked list of free disk areas. Each entry contains a pointer to the start of a free region and the number of blocks.
Cost: Fragmentation over time; extra disk operations for pointer updates during allocation/deallocation.
Indexing
Free space managed as a special system file storing addresses of all free blocks in an indexed structure. Efficient for all file allocation methods.