Memory and Storage Device

A storage device is any computing hardware that is used for storing, porting and extracting data files and objects. It can hold and store information both temporarily and permanently, and can be internal or external to a computer, server or any similar computing device.
A storage device may also be known as a storage medium or storage media.

There are two different types of storage devices:

•Primary storage devices:

Generally smaller in size, these are designed to hold data temporarily and are internal to the computer. They have the fastest data access speed, and include RAM and cache memory.

•Secondary storage devices: 

These usually have large storage capacity, and they store data permanently. They can be either internal or external to the computer, and they include the hard disk, optical disk drive and USB storage device

Primary Data Storage 

i.    RAM

It is called Random Access Memory because any of the data in RAM can be accessed just as fast as any of the other data.  A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory.  

There are two types of RAM:

1. DRAM(Dynamic Random Access Memory)

2. SRAM(Static Random Access Memory).

ii.    ROM

 This memory is used as the computer begins to boot up. 

• Small programs called firmware are often stored in ROM chips on hardware devices (like a BIOS chip), and they contain instructions the computer can use in performing some of the most basic operations required to operate hardware devices. 

• ROM memory cannot be easily or quickly overwritten or modified.

iii.    Cache

 Cache is a high-speed access area that can be either a reserved section of main memory or a storage device. 

• Most computers today come with L3 cache or L2 cache, while older computers included only L1 cache.

Secondary Data Storage

i.    Hard Disk 

The hard disk drive is the main, and usually largest, data storage device in a computer.
• It can store anywhere from 160 gigabytes to 2 terabytes.
 • Hard disk speed is the speed at which content can be read and written on a hard disk.
 • A hard disk unit comes with a set rotation speed varying from 4500 to 7200 rpm.
 • Disk access time is measured in milliseconds.

ii.    Magnetic Tape 

A magnetically coated strip of plastic on which data can be encoded.
 • Tapes for computers are similar to tapes used to store music.
 • Tape is much less expensive than other storage mediums but commonly a much slower solution that is commonly used for backup.

iii.    Optical Disc

Optical disc is any storage media that holds content in digital format and is read using a laser assembly is considered optical media.
 

The most common types of optical media are

    a)    Blu-ray (BD)

Blu-ray or Blu-ray Disc (BD) is a digital optical disc data storage format. It was designed to supersede the DVD format, and is capable of storing several hours of video in high-definition (HDTV 720p and 1080p) and ultra high-definition resolution (2160p). 

The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4 and Xbox One.

    b)    Compact Disc (CD) 

Stands for “Compact Disc.” CDs are circular discs that are 4.75 in (12 cm) in diameter. The CD standard was proposed by Sony and Philips in 1980 and the technology was introduced to the U.S. market in 1983. CDs can hold up to 700 MB of data or 80 minutes of audio. The data on a CD is stored as small notches on the disc and is read by a laser from an optical drive. The drives translate the notches (which represent 1’s and 0’s) into usable data.
    

    c)    Digital Versatile Disc (DVD)

A digital versatile disc (DVD) is an optical disc storage medium similar to a compact disc, but with enhanced data storage capacities as well as with higher quality of video and audio formats. Developed by Sony, Panasonic, Philips and Toshiba in 1995, the DVD is widely used for video formats, audio formats as well software and computer files.

iv.    Memory Card

An electronic flash memory storage disk commonly used in consumer electronic devices such as digital cameras, MP3 players, mobile phones, and other small portable devices.

• Memory cards are usually read by connecting the device containing the card to your computer, or by using a USB card reader.