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Jan's Computer Basics:

Storage: Disk Capacity

The capacity of a magnetic disk depends on several factors.

We always want the highest amount of data stored in the least possible space. (People are so greedy this way!) So the capacities of storage media keep increasing while cost keeps decreasing. It's a lovely situation for the user!

Capacity of a Disk depends on:

1. # of sides used:

single-sided disk gif


double-sided disk gif

2. Recording density -

how close together the bits can be on a track sector of the innermost track

density on disk gif

3. # of tracks on the disk

number of tracks on disk gif

Capacity of Disks

5� floppy gif 5¼" floppy - 360 KB or 1.2 MB
3� floppy gif 3½" floppy - 720 KB or 1.44 MB
Western Digital hard drive
Hard disk
      early ones = 20 MB
       [Feb. 2018]
up to 4 TB Internal hard drive
where 1 TB  = 1 terabyte = 1000 GB

The future???

Advances in technology for the read/write head and for the densities on the disks are bringing larger and larger disk capacities for about the same price. In fact, you cannot find a small capacity drive to buy, even if you wanted one! 4 TB drives are plentiful (Feb. 2018) and for the same price that we used to buy 1 Gig drives (as low as under $100). It's enough to make you cry to think of what we paid over the years and what we could get for those dollars today. Ah, well. That's the way the computer world works!