| Processing speed - high | high | High | in | low | Low |
|---|---|---|---|---|---|
| CPU | register | Cache area | RAM | Disk | CD-ROM, U disk, other storage |
| storage space- | kb | Mb | Gb | 500Gb | Tb |
CPU: Central Processing Unit (CPU, Central Processing Unit) is a VLSI, is a core operation of the computer (Core) and the control center (Control Unit). Its main function is to explain the computer instructions and data processing computer software.
The processor includes a central arithmetic unit (arithmetic logic unit, ALU, Arithmetic Logic Unit) and a cache (Cache) and a link between them for data (Data), a control and status bus (Bus). It is the internal memory (Memory) and input / output (I / O) devices are collectively referred to the three core member computer.
Register: is part of a central processing unit (CPU) in the limited memory capacity of a high-speed storage means (kb level in a relatively small space), for temporarily storing commands, data and addresses. When the CPU for processing data in memory, often take the first data into the registers, and then disposed of, and accelerate the same memory read command speed reading and writing data directly.
Cache memory: memory is present between the CPU and the memory capacity is relatively small, but a much higher rate than the memory (register slower than 1 times, but the space can be achieved MB level), close to the speed of the CPU. Cache is to accelerate reading speed of a bridge (tool). When the CPU to the memory read data, first check whether there are corresponding data buffer, if there is a direct reading, no longer read from memory. All data stored in the cache memory, which is part of the CPU to access data more frequent portions. The system dynamically manages the data in the cache, if there is data access frequency is reduced to a certain value, it is removed from the cache, memory access and replace the data into more frequent. (Cache can not only level, can have multiple level cache)
---- is often used because the cache is RAM (i.e., out of the power-off non-persistent storage), so that after use will or files to a permanent storage in a hard disk memory. The computer is the biggest cache memory, and is fitted with the fastest CPU L1 and L2 cache, graphics memory is used to cache chip card operation, there are 16M or 32M cache on your hard disk.
CACHE in the CPU is very block, and a memory capacity is small, it is the most powerful computer memory storage. Due to technical limitations, it is difficult to enhance capacity.
Memory: is stored in the main computer is running, for storing instructions (compiled code segments), each of the operating static, dynamic, temporary variable, external file pointer or the like. All programs running on the computer are performed in memory, thus affecting the performance of computer memory is very large, for temporarily storing operation data in the CPU data, the external memory and a hard disk exchange, would require arithmetic CPU the data transferred to memory, perform an operation, when the operations are completed and then the result is transmitted out of the CPU, the memory operation also determines the stable operation of the computer. The aforementioned registers and cache memory speed only accelerated the intermediate member, the operation of the original document are certainly added to the first memory, so the memory size determines the maximum size of a program to run, but the memory slower than cache 10 or so times, but space may reach GB level, or even higher.
Example: If the memory size is 4G, a program into memory requires more than 4G is space, the program is not running, of course, is also practical to remove the memory occupied by the operating system, and therefore can not be satisfied even 4G. (Of course, now have virtual memory, which is part of the hard drive is mapped memory space, less frequently accessed instructions into virtual memory, this is in fact larger than 4G of the support program, but here in the assumption that no virtual memory illustrated) under.
Virtual memory: the hard part is mapped to memory space.
Both the memory Memory in a professional name, is generally divided into a read only memory (ROM) and random access memory (the RAM) , read-only memory is widely applied, it is usually in an integrated hardware-readable chip, role is to identify and control hardware it is characterized only be read, not written.
Memory is random access memory, which is characterized readable and writable, after a power failure all data is gone.