Posted by admin on 12th March 2010

Storage Devices

Storage devices hold data in files. Any item of hardware that you can put files onto is a storage device. Some people get confused because sometimes it seems like it’s “inputting” something new to the computer when you connect a pen-drive, when in reality, it’s bringing files saved on a different computer.

Storage is measure in Bytes. A Byte (1B)is about how much a single letter in a text file takes to store. A few paragraphs might take a Kilobyte (1KB) to save – 1024 Bytes. Images normally take up a few hundred KB, up to a Megabyte (1MB) – 1024KB. Audio tracks take a few MB, but videos can quickly add up to a Gigabyte (1GB), which is 1024MB. About thousand times bigger is as much storage as you’re likely to come across this year – a Terrabyte (1TB) is 1024GB.

Storage devices can use different technologies to save files. Some use magnetism, others use light or even microchips to store data.


Some of the first computer storage devices used magnetism. The floppy disk was very important for removable storage in the early years of the PC, though by 2000 it became much less useful, as it can only store a little data – 1.44Mb.

Hard disks use a similar technology, though it’s incredible how much more data can be crammed into one. Up to a few TB can fit into a disk that’s about 15cm in diameter. The technology keeps being refined so more and more data can fit into the same tiny space – it seems to double every 18 months or so!


So how do you use light to store data? With CDs, DVDs and BluRay disks, data is encoded onto the reflective disk surface as bumps and dips at a microscopic level. When the laser in the disk drive is shone on the disk, it bounces off differently depending on whether it shines on a bump or flat area. This is why they are called Optical storage - it’s laser light that reads the data.

Each new technology makes the bumps smaller and the laser more accurate to store more data on a disk. A CD can store around 700MB, a DVD 4.7GB or 8.5GB and Blu Ray can store up to 100GB.

CD ROMs, DVD ROMs and most Blu Ray disks are Read Only Memory (ROM). This means you can only read files from the disk, not change or replace them. CD-R (and DVD-R) are Write Once, Read Many disks (WORM) – you can burn files on one occasion only, but then read them in lots of computers over and over again. CD-RW (and DVD-RW) can be burnt and then blanked to re-use over and over again, but are not true RAM (Random Access Memory) like a hard disk, where any part of the disk can be re used without blanking the rest.


There are three types of storage that use chips to store data. One is removable and used to carry files around, the others are built in to every computer.

Flash storage includes the USB “memory sticks” or “pen drives” that we use for school and that you can get cheaply anywhere. It also includes little cards for phones and cameras with strange names like SD, XD, CF and others. This has become the most common removable storage device in the last 5 years, as prices have come down and storage capacity has gone up. You can now get flash storage in 16GB and even 32GB sizes that are still small enough for your phone or key-ring!

RAM is built into your computer as the computer’s working memory. It’s much faster than other storage devices as it has a direct channel to the processor. However, as it loses all the data stored on it when the computer turns off or restarts, it’s only useful for storing what is currently open on the computer – programs, files, web-pages. More RAM means more programs can run quickly – especially important if you play games. You may have between 1GB and 4GB or RAM in your computer.

ROM is also built into your computer. It stores the code that starts your computer up, called the BIOS. It is only used for a few seconds as you start the computer up, but it’s got a really important role in making sure everything works properly.

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