I've read from this How data is physically stored in hard drives, that the North/South orientation of the magnetic medium represents data as 0 or 1 physically in the hard drive. Data is stored in binary, which means that it can be stored as either 0 or 1 in the hard drive. But what determines if that particular block of memory in the hard drive is "Used Space" or "Free Space".
In the OS, you can view how much memory is used, and how much is free.
Let's say i have a 1 TB hard drive. I stored 100 GB worth of data with the repeating pattern "1100 1100". This means that I have 100 GB of used space and 900 GB left of free space (does it?). How does it know that it is used or free? If both 1 and 0 can be used to represent the data in that block of memory, then what represents as a "Free Space"? What if i delete 50 GB of data? I'll have 50 GB more free space, but what represents this free space? And how is the data 1 or 0 of "Used Space" converted to "Free Space"?