A computer stores data using several different methods. Memory, also referred to as primary storage, typically refers to storage that is directly accessible by the computer's CPU. RAM is a high-speed storage medium that can be accessed with minimal delay. Because the RAM is connected directly to the CPU via the memory bus, the CPU can access data stored in RAM very quickly. For this reason, RAM is used to store data loaded by active programs and the operating system. RAM is a type of volatile memory because it will lose its data if the power is turned off. ROM or Read Only Memory is a type of non-volatile memory which means it keeps its data even if the power is turned off. However typically data in ROM cannot be changed. Computers use ROM memory when starting up and contains just enough instructions to get the computer going. Virtual Memory is stored in secondary storage, typically on the hard drive and is used when the RAM is full. Because the hard drive is much slower than the RAM it takes the CPU much longer to get to this information.

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Useful as an introduction showing how computers store information, and the differences between primary and secondary storage. Can be used as part of a practical activity where students are given examples of the different types of storage in class. If students are allowed to, have them look at the performance section of their computer's task manager, which shows the current usage of the RAM. For ROM restart a computer in school and have a look at the BIOS screen. Discuss why this looks so much simpler than the operating system. For an example of virtual memory, have students open a web browser and specific websites and test how long it takes to load. Then have them open a range of files/programs (to fill up the RAM) then see how long it takes to open the web browser and the same web page.