Storing data is an important part of a computer system. The main concern of all computer designers is to create fast and efficient storage devices. The computer ROM does not have enough capacity to store data, whereas the RAM is volatile and looses data once the power is turned off.
So if there is a need to save data from getting lost, it can be put on a storage device like floppy disk, hard disks and CD-ROMS before switching off the Computer.
Therefore there is a necessity for devices that could store data permanently.
Previously data was stored in punch cards (a card with holes punched representing 1s and 0s) before the invention of magnetic storage devices and then optical storage devices. With the improvement of technology it was possible to manufacture devices that could store data in excess of 250 gigabytes (1 bit is a 1 or a 0, 8 bits is 1 byte, 1073741824 bytes is 1 gigabyte).
The magnetic tape was one of the earliest forms of data storage device but had a disadvantage since it had to be accessed in a sequential manner.
The introduction of hard disk and floppy disk made it possible for data to be stored and accessed (randomly). The hard disk was not meant to be portable and was known as fixed disk located inside the computer. External hard disks were developed but not for the purpose of portability since they were fragile and prone to strong vibrations.
Portable magnetic storage devices like floppy disk had a very limited storage capacity, this was changed with the invention of the ZIP disk which could store over 100 megabytes (1048576 bytes is 1 megabyte).
The invention of the optical storage disks like the CD ROM and the DVD ROM made it possible to store data on disks which were not affected by magnetic fields, was easier to transport, and cost effective to produce.
The typical CD ROM could store around 700 megabytes whereas the DVD ROM could store in excess of 4.2 gigabytes and now with improved Blu-ray (blue laser) format storage can go up to 27 gigabytes.
The typical CD ROM could store around 700 megabytes whereas the DVD ROM could store in excess of 4.2 gigabytes and now with improved Blu-ray (blue laser) format storage can go up to 27 gigabytes.
The size of all of these disks was somewhat cumbersome (with every device invented in the modern world becoming smaller and much more portable). With this requirement new disk and memory like the flash-drive (pen drive), SD card, Compact-Flash, Sony Memory stick and the XD picture-card have emerged. Some of these devices have a capacity that could exceed 12 gigabytes and are commonly used for storage in small digital devices.
