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Data Storage

Data Storage

Author: Sophia Tutorial
Description:

Recognize how data is stored in memory.

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what's covered
When data enters a computer it is immediately routed and stored in memory. If the data needs to be kept for future use, it must be saved to a storage device. Numerous options for storage are available for computers, each with their own set of advantages and disadvantages. In this tutorial, we will take a look at computer memory, the various storage options, and the capacities for each storage option.

Our discussion breaks down as follows:

  1. How Data is Stored
  2. Bits and Bytes
  3. Units of Measurement for Storage
  4. Common Storage Media


1. How Data is Stored

In a computer, data sent to and read from the hard disk is initially read by the hard disk controller. The hard disk controller gives the processor access to read, write, and modify data on the hard disk, CD-ROM, flash drive, and any other storage device. If the operating system needs to read or write data to a storage device, it examines the storage device to determine where to read from (file location) or where to write to. After a read/write location is obtained, the hard disk controller tells the drive to read or write.

term to know
Hard Disk Controller
A hard disk component that enables the CPU to access, modify, read, and write data to and from the hard disk, CD-ROM, and any other drive.

All data stored on a hard disk is done magnetically. If the computer needs to read data from the hard disk, it reads magnetic polarities from the hard disk. One side of the polarity is 0 (off) and the other side is 1 (on). The computer reads the 0 or 1 as binary data. Each 0 or 1 is referred to as a bit (a contraction of binary digit). This means that the computer reads data from its storage location as a binary number. For the computer to write information to the hard disk, the magnetic polarities are aligned with the hard disk’s read/write head. The read/write head then writes 0s and 1s that can be read by the computer at a later time. This means that the computer writes information to the hard disk as a binary number.

term to know
Bit
A contraction of "binary digit" — a digit containing either a 0 or 1.


2. Bits and Bytes

As mentioned above, a bit is a unit of digital data, containing a single value of either a 0 or a 1. Digital information can be very large, and thus can result in incredibly lengthy strings of 0s and 1s. A string of eight bits is known as a byte. So a byte is also a unit of digital information, and it contains eight bits.

terms to know
Bit
A contraction of "binary digit;" a digit containing either a 0 or 1.
Byte
A unit of digital data, containing a string of eight binary units (0s or 1s).


3. Units of Measurement for Storage

Similar to RAM, storage space is measured in bytes. As the capacities of digital devices grew, new terms were developed to identify the capacities of processors, memory, and disk storage space. Prefixes were applied to the word byte to represent different orders of magnitude. Since these are digital specifications, the prefixes were originally meant to represent multiples of 1024 (which is two raised to the 10th power), but have more recently been rounded to mean multiples of 1000. The table below shows various storage sizes, how they are related to bytes, and an example of media with an approximate storage size.

Prefix Represents Example Storage Device Value Contained
B Byte Byte = Eight Bits 1 Character; e.g. the letter “t” is 1 byte
KB Kilobyte 1 KB = 1,000 Bytes Two or three paragraphs of text
MB Megabyte 1 MB = 1 Million Bytes Floppy Disk One-minute MP3 file
One digital picture (four megapixel)
Four books (200 pages each)
GB Gigabyte 1 GB = 1 Billion Bytes DVD-R
Blu Ray Disc
Hard Disk
USB Flash Drive
One 650MB CD of data
256 MP3 songs
340 digital pictures
600 web pages
4,470 books (200 pages each)
TB Terabyte 1 TB = 1 Trillion Bytes Hard Disk 1600 CDs of data
230 DVDs
40 Blu-Ray Discs
262,100 MP3 songs
349,500 digital pictures
655,300 web pages
4,500,000 books (200 pages each)


4. Common Storage Media

Various storage media have their own storage capacity limitations.

Hard Drive/Hard Disk
Most of today’s personal computers use a hard disk for long-term data storage. Maximum capacity is currently around 2TB.

Solid-State Drives
The solid-state drive (SSD) performs the same function as a hard disk: long-term storage. Maximum capacity is currently around 1 TB.

Flash Drives
The USB flash drive serves as a portable and removable storage solution. Maximum capacity is currently around 256GB.

Optical Disc (CD/DVD-ROM)
An optical disc is another form of portable and removable storage. Maximum capacity is currently 900MB for CDs and 50GB for DVDs.

terms to know
Hard Disk
The location for long-term data storage when the computer is turned off, and where data is retrieved from when the computer is turned on.
Solid-State Drive (SSD)
Form of data storage that uses flash memory; all data is stored on a microchip.
Flash Drive
Form of data storage that attaches to the USB connector on PCs.
Optical Disc
A form of removable storage media that stores data on the surface of the disc.


summary
As data is generated by a computer, there must be sufficient space in which to store it. Various types of storage media are available, each with their own storage capacities, pros, and cons.

Source: Derived from Chapter 2 of “Information Systems for Business and Beyond” by David T. Bourgeois. Some sections removed for brevity. https://www.saylor.org/site/textbooks/Information%20Systems%20for%20Business%20and%20Beyond/Textbook.htm

Terms to Know
Bit

A contraction of "binary digit;" a digit containing either a 0 or 1.

Byte

A unit of digital data, containing a string of eight binary units (0s or 1s).

Flash Drive

Form of data storage that attaches to the USB connector on PCs.

Hard Disk

The location for long-term data storage when the computer is turned off, and where data is retrieved when the computer is turned on.

Hard Disk Controller

A hard disk component that enables the CPU to access, modify, read, and write data to and from the hard disk, CD-ROM, and any other drive.

Optical Disc

A form of removable storage media that stores data on the surface of the disc.

Solid-State Drive (SSD)

Form of data storage that uses flash memory; all data is stored on a microchip.