How does hard disk store digital data?

This article gives you exposure about how hard disk store/write and read data into digital format in magnetic layer over pallets of hard disk. Each hard disk is having its own storing capacity based on the number of pallets or round disk having magnetic material layer on which information is written and read. The inside components are shown in the figure given below.

In today's era, it is impossible to think any digital application that does not involve any digital information in form of reading and writing. Each digital device uses memory to store the digital data in form of binary digits like zero and one. Since invention of hard disk over the 50 years back, it is now an integrated part of any digital circuit or device, say personal computer, laptop, music player whether it is i-pad, mobile phones, pen drives and memory cards, each one of them uses same principle of writing and reading of digital data. Today's computer's integrated device called hard disk has much more capacity in GB (Gega Bytes) that even thought by our father and grandfather. Today's hard disk has incredible memory capacity in terms of thousands of CDs, DVDs. Hard disk stores uses principle of magnetism to store the digital data. These digital data can be of any type like music file, image file, text file or any software file they all use binary forms and information can be written in form of magnetism in platter.

How does magnetism helps to store the digital information?

We can take simple example to learn how does magnetism helps storing the digital data. Consider an unmagnetized iron nail and you want to convey some information about your future presence in Sunday's function at your friend's home. To convey this information to your friend, you will tell this to your friend that if nail in your mail box is magnetized, you will come otherwise you will not come. Meaning magnetized nail conveys positive response (one) and demagnetized nail conveys negative (zero) response. In the same way, digital information is written in binary digits of zero and one. Our personal computer and other devices know only language of binary. Our hard disk is nothing but a box which contains billions of microscopically small iron nails. Each iron nail is nothing but small or tiny information in form of zero and one. This is called bit and eight bits make a byte and so on. Thus binary number can be easily represented by micro iron nail with its magnetism property.
If iron nail is magnetized, it represents one (1) and if it is demagnetized, it represents zero (0). Thus 12 can be represented by 1100 means it use two magnetized nail and two demagnetized nail placed along side of each other. This is the same way hard disk store the information in digital form of binary system.

Constructional features of hard disk

Hard disk is assembly of many important components put together to work as single storage unit. Each hard disk contains shiny and circular plate called platter which is divided into billions of parts called tracks. Each part of platter is independently magnetized or demagnetized to store one or zero respectively. This magnetism will last even after power of device is switched off means platter retain the digital information intact by magnetism. Platter can be one or more in number depending on the size of hard disk and its storage capacity. Platter is simply a disk made from aluminum or glass like hard material and which is coated with thin metal layer which can be alternately magnetized or demagnetized. Hard disk is also having an arm mechanism which is having read-write head which can be easily moved back and forth over platters to read and write the digital information store by magnetism. There are two read-write head for each platter. One is for reading at top surface and second at bottom to read the bottom surface. Layer of fluid or air is used to reduce wear and tear of read-write heads. Actuator with electric motor moves the read-write head/arm. Central spindle in hard disk allow the platters to rotate at very high speed in thousands of revolutions so that information can be easily and fast accessible. Plug connection joins the hard disk to mother board/circuit board. The function of Circuit board which is underside is to control and maintain the data flow to and from the platter plates. The flexible connector is used to carry the data from circuit board to read-write head and platter plates.

How does hard disk store digital data?

How does hard disk store the data?

Once the information is stored or written in material of platter or hard disk, the important and difficult task is to retrieve it. You can imagine a finding of a single magnetized iron nail from a huge collection of unmagnetized iron nails. The unmagnetized iron nails are nothing but free space or zeros. When hard disk write the data, it does this function very smartly by storing the data in some patter on platter and they are called tracks and which is made up of sectors. File Allocation Table (FAT) is a map of information stored in hard disk, It tells which part of hard disk is free and which is still free. When you write some new files, map is executed for reference and thus free space is found in platter for new writing and same is for reading process or retrieving process.

Some safety tips for hard disk

Do not use your computer in dusty or in dirty environment as dirt or dust may damaged the platter. If some of these dust or dirt comes under the read-write head, it bounces like up and down and thus it damages platter and information too, Sometimes whole hard disk is said to crashed – disk crash/head crash. Always have a habit of backing up the data from hard disk in some other means for future reference.


Author: Godson18 Dec 2012 Member Level: Gold   Points : 3

Thank you so much for this informative article. You have very well explained how the digital information is stored in a magnetic storage device. I have been studying these things in my MCA. This article has helped me a lot in understanding the basics of storage of digital data.
Keep on writing such articles. Looking forward for more such articles.

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