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COMPUTER SCIENCE - HARDWARE AND SOFTWARE - MEMORY,STORAGE DEVICES AND…
COMPUTER SCIENCE - HARDWARE AND SOFTWARE - MEMORY,STORAGE DEVICES AND MEDIA- CHAPTER 8 /1.3.5
PRIMARY STORAGE
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RAM
Random Access Memory is primary storage that temporarily holds running programs and data for processing. It is volatile, which means it loses its contents when switched off. For embedded devices RAM holds data for processing, in general purpose computers RAM holds the OS, runs programs and data for processing. Can be written to, read from or erased.
ROM
Read Only Memory is primary storage that can be read from but not written to. ROM is non-volatile, so it keeps its memory when switched off. Tends to be smaller in capacity.
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Erasable Programmable Read Only Memory - Rom that can be erased and re-written, EPROM.
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General purpose computer - gpc, a computer used for many different applications.
Temporary store of data, can be read and written almost instantly, normally a few GBs, fixed within the computer.
SECONDARY STORAGE
Non-volatile storage that is not directly accessible by the processor that is used to hold data permanently till deleted. Some secondary storage devices are removable so can be transferred between computers.
In a gpc the it is used to hold the OS. Data must be transferred into RAM before it can be processed by the CPU.
MAGNETIC
Magnetic storage devices use electromagnets and magnetic fields to control tiny magnetic dots of data to read, write and erase data.
Magnetic devices are either tape based, in a cartridge of looped magnetic tape with magnetic dots stored in series along it, or disk based, several disks known as platters that have a magnetic coating on which the data dots are stored. Both are read with an electromagnetic reading head. The reader is also known as hard disk drives.
OPTICAL
Optical devices shine a laser beam onto a disk with a reflective surface. Data is stored on the disk in the form of indentations (pits) and raised areas (land). Optical devices generally have less capacity and slower data transfer rates than magnetic devices.
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CD - Compact Disk, an early but still used optical medium.
DVD - Digital Versatile Disk, a later, higher capacity optical medium.
Blue Ray Disk - a modern, extremely high capacity optical medium.
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More portable, but slower at data transfers and has a far lower storage capacity than a hard disk drive.
SOLID-STATE
Solid-state devices have no moving parts. They use high speed flash memory to store data. SSDs are very fast at transferring data, but generally smaller in capacity and far more expensive than equivalent hard disks.
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Solid,State Drive - SSD, a solid-state equivalent of a hard disk drive.
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USB - Universal Serial Bus, solid-state stick used to store and transfer data via the USB port on a computer.
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Drive - A drive is a medium that is capable of storing and reading information that is not easily removed like a disk.
A user must take into account several factors when choosing an appropriate medium such as capacity, data transfer rate, portability, durability and costs per megabyte.
When calculating the storage requirements for data, the user must take into account the type of data and the amount of data to be stored.
OFFLINE STORAGE
Offline storage is any non-volatile storage device or medium that is disconnected, off-line, or removed from the computer.
Typical examples include: optical media, USB / RAM sticks, external hard drives and magnetic tape.
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