Hard disks drive hdd head sector cylinder platters permanent secondary storage structure computer data magnetic tape patterns of disk's surface coating IBM 305 RAMAC advanced file spindles


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Sample Chapters from book DATA RECOVERY WITH AND WITHOUT PROGRAMMING by Author Tarun Tyagi

Chapter – 2

Introduction of Hard Disks


In today’s computer world hard disks have proved themselves as the most important part of a computer. Today hard disk is the main storage device that is most commonly used to store all type of data as well as one of the most interesting components of computer.

It will be very difficult for modern computer users to even consider what computer life would be without hard disk drives, as most of us today store billions of bytes of information in our computers.

In the very earliest computers there was no storage at all. Each time you wanted to run a program you would have to enter the program manually. Even more than that, it made most of what we consider today to be computing impossible, since there was no easy way to have a computer work with the same data over and over again. It was quickly realized that some sort of permanent storage was necessary if computers were to become truly useful tools.

The first storage medium used on computers was actually paper. Programs and data were recorded using holes punched into paper tape or punch cards. A special reader used a beam of light to scan the cards or tape. Where a hole was found it read a "1", and where the paper blocked the sensor, a "0" or vice-versa.

Though it was a great improvement over nothing but these cards were still very inconvenient to use. You basically had to write the entire program from scratch on paper, and get it working in your mind before you started trying to put it onto cards, because if you made a mistake you had to re-punch many of the cards. It was very hard to visualize what you were working with.

The next big advance over paper was the creation of magnetic tape. Recording information in a similar to way to how audio is recorded on a tape, these magnetic tapes were much more flexible, durable and faster than paper tape or punch cards.

Of course, tape is still used today on modern computers, but as a form of offline or secondary storage. Before hard disks, they were the primary storage for some computers. Their primary disadvantage is that they must be read linearly; it can take minutes to move from one end of the tape to the other, making random access impractical.

Well coming back to our topic. IBM introduced the very first hard disk that would be feasible for commercial development. It was not like disk drives that are used now days. They used rotating cylindrical drums, upon which the magnetic patterns of data were stored. The drums were large and hard to work with. The first true hard disks had the heads of the hard disk in contact with the surface of the disk. This was done to allow the low-sensitivity electronics of the day to be able to better read the magnetic fields on the surface of the disk but manufacturing techniques at that stage of time were not nearly as sophisticated as they are now, and it was not possible to get the disk's surface as smooth as it was necessary to allow the head to slide smoothly over the surface of the disk at high speed while it was in contact with it. Over time the heads would wear out, or wear out the magnetic coating on the surface of the disk.

As a critical discovery of new technology of IBM in which, contact with the surface of the disk was not necessary, took place it became the basis of the modern hard disks. The very first hard disk of this type was the IBM 305 RAMAC (Random Access Method of Accounting and Control) introduced in September 13, 1956. This hard disk could store five million characters that were approximately five megabytes with the data transfer rate of 8,800 bytes per second.

In 1962, IBM introduced the model 1301 Advanced Disk File. The key advance of this disk drive was the creation of heads that floated, or flew, above the surface of the disk on an air bearing with reducing the distance from the heads to the surface of the disks from 800 to 250 micro inches.

In 1973, IBM introduced the model 3340 disk drive, which is commonly considered to be the father of the modern hard disk which had two separate spindles, one permanent and the other removable, each with a capacity of 30 MB. IBM's model 3370 introduced in 1979 was the first disk with thin film heads. In the same year IBM introduced model 3310 which is the first disk drive with 8" platters, greatly reduced in size from the 14" that had been the standard for over a decade.

The first hard disk drive designed in the 5.25" form factor used in the first PCs was the Seagate ST-506. It featured four heads and a 5 MB capacity. IBM bypassed the ST-506 and chose the ST-412--a 10 MB disk in the same form factor--for the IBM PC/XT, making it the first hard disk drive widely used in the PC and PC-compatible world.

In the year 1983, Rodime introduced RO352, the first disk drive to use the 3.5" form factor, which became one of the most important industry standards. In 1985 Quantum introduced the Hardcard, a 10.5 MB hard disk mounted on an ISA expansion card for PCs that were originally built without a hard disk.

In 1986 Conner Peripherals introduced the CP340. It was the first disk drive to use a voice coil actuator. In the year 1988 Conner Peripherals introduced the CP3022, which was the first 3.5" drive to use the reduced 1" height now called "low profile" and the standard for modern 3.5" drives. In the same year PrairieTek introduced a drive using 2.5" platters. In 1990 IBM introduced the model 681 (Redwing), an 857 MB drive. It was the first to use MR heads and PRML.

IBM's "Pacifica" mainframe drive introduced in 1991 is the first to replace oxide media with thin film media on the platter surface. In the same year Integral Peripherals' 1820 is the first hard disk with 1.8" platters, later used for PC-Card disk drives. In the year 1992 Hewlett Packard introduced C3013A which is the first 1.3" drive.

There are a number of developments that took place in the history of hard disks to give the current design, shape performance and capacities to the today’s disks. These are difficult to count in detail within this book.


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