What is the difference between a external hard


What is the difference between a external hard drive, usb hard drive, and hard drive?

A "regular" hard drive is a hard drive without any case or power supply - a bare drive - as the example WD Black from Amazon
This disk is frequently mounted inside the computer case with power lines and data lines all internal to the computer. This is known as a "bare drive" or an "internal drive" and it can be in both desktops and laptops.

They are contained inside metal or plastic cases which have interfaces built in and these are called "external hard disks", external drives" etc. The interfaces contained within the boxes (caddy or [disk] enclosure) enable the HD's interface (these days usually a SATA type) to a USB socket. A USB cable then connects the whole external HD to the computer's USB port. This USB cable in the case of 2.5" inch HDs usually supplies power the HD; for the case of 3.5" external HDs usually an external PSU is needed. These are also known as USB had drives.
There are in-between styles as well. As a basic component they take the bare, regular, or internal hard disk drive, assembled in a "clean" room and sealed in a metal case. as the essential element. Then these have an electronic circuit board to control the drive and an interface to the outside enabling power and data transfer. For an external HD there must be an interface to USB though in special cases others exist. It is possible to connect an internal HD outside the computer using a combination of cables and interfaces - you might use a USB interface while powering up the HD from the computer's internal PSU for example.
An example of what is inside a caddy (the PSU is usually external in either case) is shown from Amazon, with cables. This is a universal type without any case (wayzon)

I hope all that is clear. The essential elements are common, it's just differences in naming and assembly of two or three parts.

10.March.2015

If you go into Computer Management and go to Storage > Disk Management. You'll see the partition there. Right click on it and assign it a drive letter. You will be able to access it from there.

External hard drives contain a power supply to operate a standard hard drive in a case. It usually connects to a USB port. Usb drives get their power from the wire that connects it to the USB port A regular internal hard drive gets it's power from the computer's power supply wiring. The data cable is either a flat ribbon cable or a 6 pin cable that connects directly to the mother board.


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