What is hard Drive or permanent memory and its power units.

A hard disk or hard drive abbreviated as HD or HDD , HD is non-volatile memory .Non-volatile memory means data does not lose when PC turn OFF.it is usually install in a computer or attached directly to disk controller of the computer bord.HD contains one or more platters .data is written to the platters using a magnetic head ,which moves rapidly. Data search depend on head if head move more fast then data also search fast .if head move slow the data search on HD are slow .

internal hard disks reside in a drive connected to the motherboard using an ATA ,SCSI OR SATA cable. They are powered by a connection to the computer’s (power supply unit).

Can a computer work without a hard drive?

no Without hardisk coputer does not work .because OS store in HD and if HD not installed in system

then system does not work.

Hard drives in modern computers

Modern computers often use an SSD(solid-state drive) as the primary storage device, instead of an HDD. HDDs are slower than SSDs when reading and writing data, but offer greater storage capacity for the price.

What are the sizes/capacity of hard drives?

HDD is often capable of storing more data then other drive, HDD size depend open its size .old HDs memory size were MBS to several GB. Now HD drive have storage size of GBs to TB. every year HD technology increasing hard drive storage sizes.