Secondary memory devices or , secondary storage devices
The devices which are used to store large amount of data permanently. This is because the permanent memory , ROM, is very costly.
Types of Secondary Devices
Some secondary devices are :-
1. Hard disk
2. Compact disc
3. Digital world trade style disc
4. Pen drive or flash drive
5. Blu ray disc
6. Memory stick aur card
1. Hard disk
It consists of magnetic disks called platters.
Information is stored as tiny magnetic spots.
It is a magnetic storage media standard sizes are in TB.
The platters and associated components such as motors, head , electronic circuits and are assembled in a single unit called Hard Disk Drive.
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| Image of HDD |
Compact disk
Compact disk is an optical storage media.
The short form of compact disk is CD.
Standard capacity is 700 MB.
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| Image of CD |
DVD
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| Image of DVD |
DVD stands for digital versatile disk.
It is also called Super density Disc or SD.
It is also and optical storage media.
More storage capacity and much faster than CD ROM.
4. Pen drive or flash drive
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| Image of Pen drive |
It is solid States memory like primary memories.
These are available in the sizes of up to 256 GB.
5. Blu ray disc
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| Image of Blu ray disc |
It came after DVD .
It has more capacity than DVD.
6. Memory stick or card.
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| Image of Memory card |
It is a type of removable memory card for example in digital cameras , smartphones, camcorders etc.
Available in 4 GB to 128 GB size.
Difference between primary memory and secondary memory
| Primary memory | Secondary memory |
|---|---|
| Direct Access by CPU | In Direct Access by CPU |
| Volatile (RAM) or nonvolatile (ROM) | Non Volatile |
| Fast | Comparatively slow |
| Used for processing data | Used for storing data |
| Small size | Large size |
| Higher cost per bit | Lower cost per bit |
| Only solid state (semiconductor) | Magnetic optical or solid state |
| No moving parts | Moving parts in magnetic and optical units |