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STORAGE, FILE CONCEPTS, FILE ORGANIZATION, UTILITIES  - Part 2 -

(Pages 16-19, 194-199, OFF25-OFF37 - Discovering & Microsoft Office 2016)

Continued from previous outline

II. One of the earliest forms of PC storage is . Magnetic storage introduced us to hard drives, floppy diskettes, and .

B. How does magnetic storage work? The surface of magnetic media ( or metal) is covered with a special finish called magnetic oxide coating. Utilizing the magnetic oxide coating, the surface of the plastic or metal basically becomes magnetized. The we create is converted into magnetic particles. The magnetic oxide coating functions as a magnet to draw and retain the magnetic particles (our data) to the disc surface. Mystery revealed.

Life expectancy for data recorded on magnetic media is approximately 3 years. Why such a short time? The magnetic oxide coating diminishes over time through simple wear and tear. When the magnetic oxide coating weakens it can no longer retain the magnetic particles (our data) thus causing the particles to be released and lost. Bummer.

Examples of magnetic storage media:

1. Magnetic tape – tape is comprised of strands of plastic (much like a ) Magnetic tape is used primarily as a system because the access to information is very slow. Why? There is no way to pinpoint the exact location of a file recorded on tape (when needing to retrieve it), you must read all the preceding content of the tape until you locate the file you wish to retrieve.

Magnetic tape is not formatted like all other storage media. Purpose of formatting? Formatting establishes addresses and a (FAT). The FAT is like a that keeps of every file’s location.

Again, tape is not formatted so there are no addresses identifying the location of files. This is the equivalent of having to deliver the mail and the letters or correspondence you wish to deliver contains no addresses. To deliver the mail you’re forced to go door by door inquiring who lives in a residence until you find the recipient of the mail. A mailman’s nightmare.

Characteristics of tape include the following:

Fall 2016 1 a. Inexpensive, portable, large storage capacity

b. Data is stored & retrieved sequentially (one record after another – no addressing system) / slow access to information because you have to go file by file through the tape until you locate the file you need

c. Requires a tape unit or – not standard or common on PCs

d. Most PC tape units are external (USB), not typically built into the system unit

e. Assumes whatever drive letter is available (only A,B, and C are assigned)

f. Ideal for making where the primary concern is just to have extra copies of files

2. Hard disk (drive) – By far the most common magnetic storage device for personal computers, primarily because of the capacity, most hard drives store a ’s software. A hard drive (disk) is comprised of one or more metallic platters varying in size and capacity. A hard disk may be fixed (internal) or removable (external). Other hard disk characteristics Components include the following: of a hard drive

a. The hard disk surface is more durable (metal) than tape or floppies (plastic), therefore data is considered more secure.

b. The Hard Drive is a Direct access storage device (DASD) – files may be accessed randomly, unlike tape where access is sequential. This is why access to information on the hard disk is much faster.

The operating system uses the "FAT" to identify a file's location. Before a hard disk is utilized, it is first formatted. Formatting creates storage units on disk containing addresses, every time a file is saved, the file name and its storage address is recorded in the FAT. The operating system uses the FAT to pinpoint the exact location of a file, no need to check other locations like when using magnetic tape.

Fall 2016 2 Magnetic tape has no FAT, that’s why every preceding record has to be checked, the operating system doesn’t have an address to identify the location of a file.

c. A critical component of the hard drive is the “read and write” head (check diagram on previous page). The read/write head is used to record and read information from the disk surface. It functions much like a needle on a record player. If the needle is not functioning, you can’t play records.

The faster the drive's disk platter spins the faster the computer can access and record data. The speed of the drive is measured in “” (rpm).

d. Although most hard drives are internal, external hard drives are now very popular.

e. A major negative concerning the hard drive is the susceptibility of a head crash. A head crash is often fatal because it can result in loss of access to all data.

Most disk drives are guaranteed for no more than three years. Disk drives contain mechanical parts that over time simply fail (through wear & tear). The drive’s parts must all be operational to store and retrieve data. When the parts fail, there is no way to retrieve data, in essence you lose everything on your hard drive, files are no longer accessible.

A head crash can also occur when contaminants (smoke, dust, hair, etc.) enter your disk drive and come in contact with the “read and write” head. The contaminants can cause a scratch or damaging mark to be placed on an area of disk where information is recorded. Because of the damage to the disk, the data in that area can no longer be read which results in the loss of data. Much like when you have a scratch on a record (LP) or music CD, a scratch can result in loss of the access to recorded music. If the contaminant damages the read/write head, major problem, data is no longer accessible. Fluctuations in electrical power can also contribute to a head crash if it results in scratches made to the disk while in the process of writing to the disk.

A head crash does not delete data, a head crash means that the mechanical components of the disk drive are no longer functioning thus making it impossible to retrieve data.

f. Hard drives are typically identified as drive C:

g. Hard drives provide the largest capacity of all PC storage devices, 4-10 TB

3. Floppy diskettes (legacy device) – Floppies consist of a round piece of plastic protected by an outer covering. Floppies vary in size and storage capacity. Before CDs & flash drives, everybody used floppies. Early PCs had no hard drive, most PCs functioned with 2 floppy drives (A: & B:).

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a. 5.25 Double sided double density (DS/DD) can store up to 360 KB (wow)

b. 5.25 Double sided high density (DS/HD) can store up to 1.2 MB

c. 3.5 Double sided double density (DS/DD) can store up to 720 KB

d. 3.5 Double sided high density (DS/HD) can store up to 1.44 MB

e. Very inexpensive but provide very low storage capacity

f. Provide direct access to data (DASD)

g. Media is portable or mobile

h. Typically identified as drive A: and drive B:

C. – Information recorded on an optical disc is written with , not the magnetic employed by magnetic media. Lasers in essence "burn" information onto the storage disc

Data recorded on optical media is considered less susceptible to environmental damage (dust, hair, smoke, etc.). Optical storage has far greater storage capacity than removable magnetic media (floppies). A typical CD ROM, CD-R, or CD-RW can store approximately 700 MB, a DVD has capacity. Data on optical storage can be retained for over 30 years. Advances in technology provide even greater capacity for

Fall 2016 4 optical media, as in the case of Blu-Ray . The different types of optical discs are identified below:

1. CD-ROM – “ Read Only Memory” - contains permanent, unalterable information – comes with prerecorded information that cannot be altered

2. CD-R – “Compact Disc Recordable” - data can be written onto the disc, once initial recording is completed, cannot be deleted or modified– If you want to record on a CDR disc you need a recordable CD drive

3. CD-RW – “Compact Disc Rewriteable” allows the user to record, erase, and modify the disc content several times as desired, in that sense, functions like magnetic media – on the contrary, CD-R discs can be written to only once.

4. DVD – “Digital Disc” - contains gigabyte capacity. A DVD drive can read CDs but a CD drive cannot read DVDs. DVDs can be either “read only” or “recordable”. Many new exist providing greater capacities (HD-DVD, Blu-Ray DVD) DVD drives can recognize any type of optical disc, be it CD or DVD. This makes DVD drives the most versatile storage device.

5. Disadvantage: Slow read and write time. The read and write speed of optical drives is measured at 150 KB per second. Read and write speeds for optical drives are identified by a number, 6X, 10X, 20X, etc.

What do the numbers represent? The read/write speed of the drive. Again, the original drive had a read/write speed of 150 KB per second. The number to the left of the (X) represents the improvement over the original speed. If a drive is identified as 6X, it means the speed is 900 KB per second (150 KB x 6) – Read and write time is slow when compared to most magnetic media & solid state storage.

6. Assumes whatever drive letter is available (only A,B, and C are assigned)

D. Solid state storage () – a relatively new concept in storage which offers several advantages. Faster, durable, compact, and portable. If contrasted with other forms of storage, for byte Solid State is more expensive. USB or flash drives are popular solid state devices. PDAs, cell phones, and cameras also use solid state media. Devices are independent of a drive, devices contain no moving parts; therefore, no head crash can occur. As mentioned before, a

Fall 2016 5 head crash is a major problem associated with hard drives. There are no head crashes in Solid State storage, it’s not possible.

Flash drives can hold up to GB capacities and again, require no investment in a storage drive nor do they occupy a drive bay (explained later). You must properly eject or remove a to avoid damage to the drive’s contents. Life span of data on Solid State, about 10 years. Through wear and tear, devices do malfunction.

Flash memory devices assume whatever drive letter is available (only A,B, and C are assigned)

1. Solid state hard drives provide the best of 2 worlds, large volume capacity and speed. Common in mobile devices.

E. ?

1. OneDrive – Microsoft email accounts provide free cloud storage. There are other free Cloud Storage drives: Google Drive, iCloud, etc.

Advantage? Free voluminous storage accessible anywhere you have access to the Internet.

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Disadvantage? You need access to the Internet, security vulnerabilities, data can be compromised if not protected well.

2. Others – An Internet search of “online storage” will identify many sites of free and “for pay” Cloud storage.

F. A system unit contains several drive bays used to house internal storage drives. The drive bays are located at the front of the system unit (basically a slot in the case for inserting the drive).

Drive Bays

The significance of drive bays has diminished with the advent of USB technology, today we have practically any type of storage device that can be connected through a USB port outside the system unit, no drive bay is needed to house the drive.USB ports can be located in the front or back of the system unit, or even in the monitor.

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