What Happens on hard drive When You Click "Save"?
by: kuberdeals
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What Happens on hard drive When You Click "Save"?
Pretend you are writing a letter in Microsoft Word. Here's a very simplified version of what happens when you click the "Save" command.
1. Microsoft Word tells the operating system (such as Windows '98) to store your letter in the hard drive.
2. Your letter, which is currently hanging out in the computer's main memory (located on the motherboard), hops on the hard drive interface, and rides it to the hard drive's cache buffer.
3. Upon arriving in the cache buffer, your letter is met by the hard disk controller.
4. The hard disk controller receives a communication from the operating system: "Controller, please store the document at this address: ****."
5. The read/write heads move into position over the correct track and wait for the correct sector to pass under. As soon as it does, the elected head starts writing the letter onto the elected platter.
But what if the document is really huge and can't fit onto one sector? If the next sectors on the track are empty, the drive will continue writing the document there. If the track fills up and there is still more writing to be done, however, the drive's first choice will be to switch heads. Since the heads all move in unison, all the other heads are positioned over the same track on their respective platter surfaces. It is faster to use an alternate head than to reposition the heads over a new track. A sequential group of tracks is referred to as a cylinder, because they are one on top of another, not side by side.
This brings up another interesting point. After you've owned a hard drive for a while, the availability of long sequential platter space grows scarce. Things start getting messy as you throw files away and add new ones. When this happens your hard drive is said to be fragmented. As a hard drive becomes more and more fragmented it loses efficiency because it is forced to spend more time repositioning its read/write heads. However, you can do what's called defragmenting your hard drive. You just need a defragmenting program, which isn't expensive. The program will reorganize the data on your hard drive for optimum efficiency.
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