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The need for virtual memory

• The definition: Virtual memory is a section of volatile memory created temporarily on the storage drive. It is created when a computer is running many processes at once and RAM is running low.
• Virtual memory is much slower than main memory BECAUSE processing power is being taken up by moving data around, rather than just executing instructions. The guide on operating systems explains how the OS manages memory. Using virtual memory slows the computer down because copying to a hard disk takes much longer than reading and writing RAM.
• If your computer lacks the RAM needed to run a program or operation, Windows uses virtual memory to compensate. Virtual memory combines your computer's RAM with temporary space on your hard disk. When RAM runs low, virtual memory moves data from RAM to a space called a paging file.
• Swapping (also called paging) is the process the OS uses to move data between RAM and virtual memory. The OS moves data from processes that are not immediately needed out of the RAM and stores them in virtual memory. It copies the data back into RAM when the process is needed again.

Cache memory

• The definition: Cache is a small amount of memory which is a part of the CPU - closer to the CPU than RAM. It is used to temporarily hold instructions and data that the CPU is likely to reuse.
• Not a lot of physical space is allocated for cache. There is more space for RAM, which is usually larger and less expensive.

Flash memory

• The definition: Flash memory is a type of non-volatile memory that erases data in units called blocks. A block stored on a slash memory chip must be erased before data can be written, or programmed, to the microchip.
• non-volatile memory is typically used for the task of secondary storage, or long-term persistent storage. The most widely used form of primary storage today is a volatile form of RAM meaning that when the computer is shut down, anything contained in RAM is lost.

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