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Memory explained

memorycard.jpgOne feature that is usually found on mobile devices spec sheets is the amount of memory. Unfortunately, there’s often only one type of memory shown, and it’s not always obvious which type it is. In order to know exactly what a handset can support, it’s useful to know the different types of memory that each devices can have.

Asking how much memory a phone has can actually result in multiple, different answers, and to make things harder a lot of web sites confuse the different types. In general, these are the types of memory a phone can have:

  • ROM: This is non writable memory, containing the basic operating system of the phone. When you do a hard reset and format the memory of the phone, what’s on the ROM is what stays and why your phone can always be reset to factory settings. The amount of ROM a phone has is irrelevant since you can’t add things to it.
  • Flash / internal memory: The amount of internal memory, sometimes called flash memory, is the space inside the phone where programs reside and where you can store messages, contacts and files. It’s usually the number you see when you look at a phone description and it says, for example, that the Nokia 6620 has 12 Megs of memory. If you are trying to save data such as a game on your phone and your phone complains about memory issues, this is probably what it needs.
  • RAM: This is the temporary memory used to run programs. It must not be confused with the flash, since it can’t be used to store data. The memory is cleaned every time the phone is turned off. This is very rarely written in descriptions, but it’s very important since it dictates how many programs you can run at once. Some tools can tell you the number, such as FExplorer for S60 phones. The 6620 has 26 Megs. In some devices, built in flash is used for both internal memory and RAM. When trying to run a program, if it complains of memory issues, or closes due to running out of memory, this is what it needs. Note that the operating system itself as well as other running applications use up RAM and it’s often possible to free some more memory by closing applications or sometimes with firmware updates.
  • External memory: This is simply the external memory cards that can be added to the phone. Many phones have extension slots now, but you need to be aware of the maximum size they support (512Megs, 1G, 2G, 4G and so on), and also the type (MMC, MSD, MiniSD, MicroSD and so on). There are not a lot of differences between the various types other than physical size and power consumption. Some recent models also introduced some DRM (copy protection) capacities.
  • SIM: A SIM card is the little card used in GSM phones to store your phone number and contact information. These cards also have memory that can be used to store information. Usually it’s limited to contacts and sometimes a small amount of messages. The memory size can be tiny, such as 64KBytes, but it can be useful to transfer contact lists between phones.

When shopping for a phone, especially a smartphone, it’s important to have all the numbers. For example, a Nokia N80 has less free RAM than a N73, and will have more problems running multiple applications, even if both are modern smartphones. It’s important to check for these numbers in specs sheets or reviews to know if the phone will meet your needs, and then you’ll be sure to never run out of memory.

 

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