What Is Hard Disk? And Its Components

Shivendra Nath



Every computer system and server contains one or more hard disks within them. A hard disk drive is a data storing hardware device that is non-volatile in nature. It means that the computer system will not lose the data stored on the Hard disk drive after removing the power supply. This enables them to store data and programs on a permanent basis.

Reynold Johnson invented the first hard disk when he was working in the IBM company. Also, it was announced on September 4, 1956, with the name of IBM 350 Disk Storage Unit. As we all know that necessity is the mother of all inventions. So, before the invention of the hard disk drive, punched cards and magnetic tape reels were in use.

The problem with both of them was that they can only be accessed serially i.e from start to end. So, let’s assume you have to read the data present in the middle of the tape. To read that you have to start reading from the beginning and this makes it slower. But the Hard drive is much faster than that and we will look into it in more depth shortly in this post.

Parts of Hard Disk Drive:

The particular Hard drive consists of moving parts in which there is a shiny silver Platter. The platter is the place where information is stored magnetically. You will also find an arm mechanism that moves the read and write head back and forth to store information on the platter. Moreover, there is an electronic circuit that controls everything. Also, that circuit connects the gap between the hard drive and the rest of the computer.

Let’s see the parts of the hard disk drive in detail below:

  1. Actuator: It is the part of the Hard Disk Drive that moves the read-write arm. The older Hard Disk Drives consists of stepper motors as actuators. On the other hand, when we talk about the modern hard drive, it uses voice coils instead of stepper motors.
  2. Read-Write Arm: This read-write arm shifts the read-write head across the magnetic platter.
  3. Central Spindle: The task of the central spindle is that, it helps the platter to rotate at high speed.
  4. Platter: These magnetic platter stores the information in Binary form i.e. in the form of Zeroes and Ones.
  5. Connection point: connection point establish the link between hard drive to the motherboard of the computer system.
  6. Read-write head: read-write head is a small magnet on the end of read-write arm.
  7. Flexible connector: This hard disk drive also contains circuit board which is mainly responsible for controlling the data to and from Platter. So this flexible connector caries the data from circuit board to the read-write head and the Platter.
  8. Small spindle: It helps the read-write arm to swing across the Platter.

More About Hard Disk Drive:

We have covered almost every part of the hard disk drive, So now let’s know more about the Platter of the Hard Disk. The main component of a Hard Disk Drive or HDD is the Platter. As the name sounds, It is made from a hard substance like Glass, ceramic, or Almunium. In addition to that, HDD is coated with a thin metallic layer, which can be magnetized or demagnetized.

[Image Representing concept
of tracks and sectors of platter]

The Platter of the Hard Disk Drive is divided into many small areas. And those areas independently store Ones and Zeroes. To store 1 that tiny area has to be magnetized and to store 0 it has to be demagnetized. Generally, HDD comes with 5400 RPM or with 7200 RPM, where RPM stands for Rounds Per Minute. One point to note that is, the more speed of the Platter the more speed of Read and Write will be there in the Hard Disk Drive.

When the computer stores the data into the HDD it stores the bits of data in an orderly manner in every Platter. And the data is stored in the tracks and sectors of the Platter. The tracks are nothing but the concentric circles on the Platter and Sectors are part of the tracks. Look at the image for better understanding at the right. The green portion represents the Track and the Blue part represents the sector of the Platter.

Better alternatives to Hard Disks:

There is another alternative to Hard Disk Drive and that is the SSD. SSD stands for Solid State Drive and it also stores the data in a permanent way just as the HDD does. However, SSDs does not contain any moving mechanical parts which make them faster than Hard Disk Drive. And there are several pros and cons of both storage technology that we will see in another post.


So we can say that the technology of Hard Disk Drives is not new in fact it is several years old. And also with the advancement of technology the size of hard disk reduced in size. Like when you look at the old Hard Disks which were much bigger in size and the hard disks now that are compact and more efficient. So, that’s all for this post and see you in the next one. Also, Leave your thoughts in the comment section below and thanks for reading the post.


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