Secondary storage.

 What does Secondary storage Device mean?

A secondary storage device refers to any non-volatile storage device that is internal or external to the computer. It can be any storage device beyond the primary storage that enables permanent data storage.

A secondary storage device is also known as an auxiliary storage device or external storage.

Here are some examples of Secondary storage Device's :

Secondary storage devices are primarily referred to a storage devices that serve as an addition to the computer's primary storage, RAM and cache memory. Typically, secondary storage allows for the storage of data ranging from a few megabytes to petabytes. These devices store virtually all programs and applications stored on a computer, including the operating system, device drivers, applications and general user data. Most of the secondary storage devices are internal to the computer such as the hard disk drive, the tape disk drive and even the compact disk drive and floppy disk drive.

Secondary Storage compared to Memory

• It is always slower to access data from secondary storage than from memory.
• Data stored in secondary storage is permanent, it is NOT lost when the computer is turned off.
• Secondary storage typically has a far higher storage capacity than RAM.

Secondary storage can be divided into three main technologies:

Magnetic devices

• These have a tape or disk surface which can be magnetised with a pattern of north and south areas to represent the binary data. As the changing magnetic surface moves past a read head it reads the alternating pattern of tiny current changes as binary digits.
• Typical examples include hard drives, floppy disks and magnetic tape.

Optical devices

• These use a circular disk surface where a spiral pattern of reflective and non-reflective areas represents the binary data as the disk surface moves past it.. A low-power laser beam tracks this spiral pattern and reflects laser light onto a light detector. The pattern of bright and non-bright reflections form a pattern which is read as binary digits.
• Typical examples include CD-ROM, CD-R and CD-RW disks, along with the higher capacity DVD and Blu-ray equivalents.

Solid state devices

• These store the binary data on semi-conductor material where a pattern of on/off semi-conductor switches represents the binary data.

• A typical example is a solid state drive.

History of Secondary storage's.

In 1956 ::

In 1956, IBM’s Data Processing Division in southern San Jose, Ca transported the first hard-drive that only held a whopping 5 megabytes of storage.

Unbelievable right?

In 2018 ::

But now take a look at this picture of a SanDisk memory card which can hold a whopping 1 Terabyte of storage, thats a lot of storage, technology has come a log way and there is a lot more to come in future as well.

                                               - D. Srikanth.