You know that both expensive and limited processor memory is also known as primary memory. The primary faster memory, too, is volatile. If we need to permanently store large quantities of data or applications we need a simpler and secure memory. These experiences are called secondary memories. Here we will discuss secondary memory devices, which can be used to store large quantities of data, audio, video and multiple.
Characteristics of Secondary Memory
These are some features of secondary memory, which differentiate it from primary memory−
Hard disk drive consists of a series of round disks called platters set around 1⁄2 inches apart around a spindle, one over the other. Disks are made of non-magnetic material such as aluminum alloy, and lined with magnetic material between 10-20 nm.
These disks have a standard diameter of 14 inches and rotate with speeds varying from 4200 rpm (rotations per minute) for personal computers to 15000 rpm for servers. Data is stored by magnetizing the magnetic layer or by demagnetizing it. Using a magnetic reader arm, data is read from and write to the disks. A typical, modern HDD has terabyte (TB) capacity.
Compact Disk stands for CD. CDs are circular disks that read and write data using optical rays, usually lasers. They 're really inexpensive, and for less than a dollar, you will get 700 MB of storage space. CDs are loaded into CD drives built into CPU cabinets. They are compact as the drive can be expelled, the CD extracted, and taken with you. There are 3 types of CDs–
DVD stands for Digital Video Display. DVDs are optical devices that can hold data held on CDs 15 times over. Typically they are used to store rich multimedia files requiring a high storage capacity. Three varieties of DVDs often come in – read-only, recordable, and rewritable.
Pen drive is a portable tool for recording data utilizing solid-state memory, rather than magnetic fields or lasers. This uses a RAM-like system, except it's non-volatile. Often classified as USB drive, key drive, or flash memory.
Blu Ray Disk (BD) is an optical recording medium used to display content in high quality (HD) and other recorded multimedia. BD requires a laser of shorter duration than CD / DVD. This helps the writing arm to work more carefully on the disk and thus pack in more details. BD's will store data up to 128 GB.