What is a Hard Drive?

Posted on January 31, 2022

A computer hard drive (or a hard disk or HDD) is one kind of technology that stores the operating system, applications, and data files such as documents, pictures, and music that your computer uses. The rest of the components in your computer work together to show you the applications and files stored on your hard drive.

Hard drives can be external or internal.

Internal Hard Disk or Fixed Hard Disk – A hard drive is a nonvolatile memory device that can permanently store information. It is fixed inside the CPU.

External Hard Disk or Portable Hard Disk – Portable hard drives as the name suggested are very useful because you can carry data anywhere and transfer information, programs, pictures, etc between devices.

Hard Disk Drive Components

  • Reading and Writing Head
  • Disk Plate on which the data are recorded
  • The engine that turns the disk plates
  • Cache
  • Electronic control unit
  • The electromagnetic component that moves the head
  • Moisture protective bag
  • Vent hole
  • Torx – Screw type component
  • The outer layer that protects from dirt and dust

Why Hard Drive is Important? Spin speed (rotations per minute, or RPM) is relatively important. The faster a disk (platter) spins, the faster your computer can find the file you want.

How to Hook Up Hard Drives on a Desktop Computer?

External Drive –

  • Plug the drive’s power adapter into an electrical outlet, and then plug the cable that comes out into the power supply of the drive itself. If the unit has a power switch, set it to the “On” position. If the drive is powered via USB, you can skip this step.
  • Connect the data cable to the appropriate port on the back of the hard drive. Most hard drives use either a USB connection or an external Serial Advanced Technology Attachment cable. In any case, it can only be inserted in one way, so it is important non-violently.
  • Plug the other end of the cable into the appropriate USB or SATA port on your computer. Once your computer recognizes the drive, it is ready to use.

Internal Drives

  • Touch a metal part of the computer chassis, such as the back panel, to break it and remove any static electricity that has accumulated in your body.
  • Shut down your computer and unplug it from the wall.
  • Remove the side and front covers of the case so that you can easily access the internal drive bays.
  • Slide the new hard drive into an open 3.5-inch drive bay and use the four mounting screws to secure it in place. If you have a 2.5-inch hard drive, or if you need to place your hard drive in a 5-inch bay, attach a set of adapter rails that connect to the sides or bottom of the drive to make it fit in the larger bay. You can then screw the rails into the mounting bay.
  • Connect a SATA data cable to the data connector. The data connector is the smaller one on the back of the drive. The piece containing the connectors inside the socket on your drive or motherboard is shaped like a capital L with a very short tail. This prevents you from inserting the cable the wrong way.
  • Connect a SATA power cable coming out of your computer’s power supply to your drive’s SATA power connector. The SATA power connector looks like the data connector but is much wider. If your power supply doesn’t have an extra SATA power connector, connect a four-pin Molex-to-SATA power adapter to a large white four-pin connector coming out of your motherboard.
  • Connect the other end of the SATA data cable to an open SATA port on your motherboard. If your computer’s motherboard is out of SATA ports, you will have to add an expansion card with additional internal ports.
  • Replace your computer’s cover and plug it back in. Your drive is now hooked up.

Types of Hard Drives

  1. Parallel ATA (PATA)
  2. Serial ATA (SATA)
  3. Small Computer System Interface (SCSI)
  4. Solid State Drives (SSD)

What is Stored on a Hard Drive?

Your documents, pictures, music, videos, programs, application preferences, and operating systems represent digital content stored on a hard drive. 

Size of the HDD

Everything stored on a hard drive is measured in terms of its file size. Documents (text) are generally very small whereas pictures are large, music is even larger, and videos are the largest. A hard drive determines the size of digital files in terms of megabytes (MB), gigabytes (GB), and terabytes (TB).1

Check –

  • Physical sizes are either 3.5″ for desktop computers
  • 2.5″ for laptops.
  • SSDs range from 1.8″ to 5.25″

How Data is stored on Hard Disk?

  1. Actuator that moves the read-write arm. In older hard drives, the actuators were stepper motors. In most modern hard drives, voice coils are used instead. As their name suggests, these are simple electromagnets, working rather like the moving coils that make sounds in loudspeakers. They position the read-write arm more quickly, precisely, and reliably than stepper motors and are less sensitive to problems such as temperature variations.
  2. Read-write arm swings read-write head back and forth across platter.
  3. Central spindle allows platter to rotate at high speed.
  4. Magnetic platter stores information in binary form.
  5. Plug connections link hard drive to circuit board in personal computer.
  6. Read-write head is a tiny magnet on the end of the read-write arm.
  7. Circuit board on underside controls the flow of data to and from the platter.
  8. Flexible connector carries data from circuit board to read-write head and platter.
  9. Small spindle allows read-write arm to swing across platter.

Should I Choose an Internal or External Drive?


It depends on your situation. Upgrading your computer’s internal hard drive provides built-in storage for all of your files. An external hard drive gives you portable, on-the-go storage at your fingertips.

History of Hard Drive

Like many innovations in 20th-century computing, hard drives were invented by IBM as a way to provide computers with readily available “random access” memory.

The problem with other computer storage devices, such as punched labels and magnetic tape reels, is that they can only be accessed in sequential order (in order, from start to finish), so the small data you want to retrieve is in the middle. on tape you have to read or scan the whole thing, just slowly to find the thing you want.

Everything is faster on the hard disk, which can move its read and write head very quickly from one part of the disk to another; each part of the disk can be accessed as easily as any other part.

The first hard drive was developed by IBM’s Reynold B. Johnson and announced on September 4, 1956 as the IBM 350 Disk Storage Unit.