Memory said a little bit, is a cache, will be free of hard disk and CPU data exchange between the bottleneck is too large and set, but now the hard disk is still a computer performance bottleneck, such as the speed of the hard disk and memory on the line.
Memory is the main part of the computer, and it is relative to the external memory. We usually use the program, such as Windows98 system, typing software, game software, etc., are generally installed on the hard disk and other external memory, but only this is not able to use its functions, you must put them in memory to run, to really use its function, we usually enter a paragraph of text, or play a game, In fact, it's all in memory. Often, we store large amounts of data that we want to keep on external memory, and put some temporary or small amounts of data and programs in memory.
In the central processing unit and hard disk play the role of transition, specifically, the CPU processing data quickly, but the hard disk is limited to its own physical structure, the speed is relatively slow, how to strike a balance between this fast and slow, resulting in memory. First, read and write the data from the hard disk into memory. The processor then processes the data in memory. Conversely, memory data can be written to the hard disk.
Simply put, if the hard disk is a big bookshelf, use it for all your books. Then the memory is like your desktop, you read which book time, you take down the book to put on the desktop to see, after reading, you will put it back to the shelf. That is, the memory is temporary storage of some computers often used and must use the program, Memory for data such as files. When the power outage (shut down) the contents of the memory are gone.