Hard Drives

A hard drive is a data storage device that uses electromagnetism to store and retrieve data stored on one or more rigid, rotating discs called "platters". These platters are coated in magnetic material, and are divided into billions of tiny areas. They are found in basically any kind of electronic machinery that can store data, from computers to the first iPhones.
The first hard drive was the IBM 350, created in 1957. It was the size of two refrigerators and could store 3.75 megabytes. For reference, a normal hard drive today weighs 8 oz, and can store 4,000,000 megabytes of data.
The IBM 350








                                  Hard drive platter

The platters on a hard drive store information by converting it to binary, a system that uses ones and zeros to identify information. Each one of these areas can be individually magnetized to make it a "one", or demagnetized to store a "zero". Once magnetized, the area will stay as such until it is purposefully demagnetized, allowing the hard drive to store data even when there is no power.

In the picture, you can see what looks like the needle arm of a record player. This is called the "read-write head", and it is a thin, horizontal, metal blade with a magnet on the end that both "reads" the binary stored on the platter and writes data in by magnetizing and demagnetizing certain parts. Modern read-write heads are so small they are measured at a nano scale. Smaller, more efficient read-write heads and platters allow for more platters to be stored within an area, and thus, more data to be stored in the same size area.
The key problem a hard drive must solve is not how to store data, but how to locate it. The hard drive must store data incredibly methodically, or it quickly becomes a game of finding the needle in the literal billions of haystacks. The hard drive solves this by storing the needles in a very orderly fashion on each platter. The data are arranged in concentric paths called "tracks", and each track is then broken down into sectors. When the computer has to store new data, it finds an open sector that doesn't have any data already stored in it. It then moves the read-write head to that sector and records the data there. The platters spin at hundreds of rotations per minute, (a modern hard drive can spin at 7,200 RPM), allowing the read-write head to access the data very quickly.
One drawback of hard drives is the fact that they have to be so precise. The smallest speck of dust can cause the read-write head to bounce on the platter, damaging the platter, and potentially erase all of the information stored on the hard drive. Hard drive damage is almost entirely irreversible. Because the platters spin at such a high speed, the heads of a hard drive can end up cutting entire canyons across a hard drive, destroying all of the data.
Hard drives are in the process of being replaced by another method of storing data, called "flash memory" or SSD. SSDs are more resilient, lighter, and more efficient at storing and retrieving data than hard drives. SSDs are the things you will find in almost all modern phones, and computers are starting to trend towards them too. However, SSDs are almost five times the price of a hard drive per gigabyte, so the hard drive won't be going out of fashion any time soon.


Flash Drive (SSD)



Links used
https://en.wikipedia.org/wiki/History_of_IBM_magnetic_disk_drives#IBM_350
https://www.explainthatstuff.com/harddrive.html
https://www.seagate.com/do-more/everything-you-wanted-to-know-about-hard-drives-master-dm/
https://express.google.com/u/0/product/16121399639429397064_2744642317472280715_125181302?utm_source=google_shopping&utm_medium=tu_prop&utm_content=eid-lsjeuxoeqt%2Ceid-wuakzuqbuq&gtim=CNrrvs_9hr7cSxDFmeWRz7WK2MgBGLDdpS0iA1VTRCiAurznBTD2utg7&utm_campaign=125181302&gclid=Cj0KCQjwoInnBRDDARIsANBVyARjtlqdZwGHulzDSjQBMN72nPjBoH-1XxNhp_-AuVNaAAPp5pM5negaApPZEALw_wcB