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Computers store temporary data in the RAM (Random Access Memory). These could be operating instructions, loose bits of data or content from programs that are running.
The contents of RAM are constantly rewritten as the data is processed.
When the computer is switched off, all the data is cleared from the RAM.This type of memory is called volatile because it only stores the data whilst the computer is switched on.
Computers need backing storage outside the CPU to store data and programs not currently in use.There are three main types of storage device:
Those that store data by magnetizing a special material that coats the surface of a disk.
Those that store data using optical technology to etch the data onto a plastic-coated metal disk. Laser beams are then passed over the surface to read the data.
Flash drives use solid state technology and store data in a similar way to the BIOS chip.
The hard disk of the computer stores the system information, programs and data that the computer uses every day.
Computer servers will use RAID systems with many hard drives to provide huge capacity and safer storage. The drives can be mirrored so that data written to one of them is also written to others, so if one drive fails, the others just take over.
Removable hard drives plug into the USB port and can be used for backup or transfer of data to another computer.
Floppy disks used to be used a lot, but they are unreliable and don’t hold very much data, so they are rarely used now.They hold 1.44 MB of data, so are only really useful for backing up or moving small files that don’t contain graphics.They are easily damaged, which means that files stored on them won’t always load.As flash memory has become cheaper, many new computers don’t even have a floppy disk drive.
There are two main types of optical storage: CD and DVD. They look exactly the same, but DVDs hold much more data than CDs and need different drives to read them.
CD-ROMs are read only – you can read data from them but can’t write more data to them.CD-Rs allow you to write data once, but you can’t write over it. CD-RWs allow you to write data and then record new data over it.DVD-Rs and RWs follow the same pattern.You need special software to write to CDs and DVDs – you cannot simply copy files to them.
In recent years, flash memory has become much more popular.
It holds a lot of data in a very small space. It doesn’t need special software to use it. Most computers will recognize the device as soon as you plug it in.Flash memory sticks connect through USB or FireWire ports.Many other devices, like digital cameras and MP3 players, also use flash memory.Flash memory cards can hold different types of data so your MP3 player could hold a data file with your homework on it, for example.