External storage refers to storage other than computer memory and CPU cache. This type of storage can generally still save data after a power outage. Common external memories include hard disks, floppy disks, optical disks, U disks, etc. (Recommended learning: phpstorm)
Common external memories of PCs include floppy disk storage, hard disk storage, optical disk storage, etc. There are two types of disks: floppy disks and hard disks. There are three types of optical discs: read-only CD-ROM, write-once optical disc WORM, and rewritable optical disc MO.
Introduction
There are many types of memory, which can be divided into main memory and auxiliary memory according to their uses. Main memory is also called internal memory (referred to as memory), and auxiliary memory is also called internal memory. It is called external memory (referred to as external memory).
The most prominent feature of internal memory is fast access speed, but small capacity and expensive price; the characteristics of external memory are large capacity, low price, but slow access speed. Internal memory is used to store programs and data that are needed immediately; external memory is used to store programs and data that are not used temporarily. Information is frequently exchanged between internal memory and external memory.
External memory is usually magnetic media or optical disks, such as hard disks, floppy disks, tapes, CDs, etc., which can store information for a long time and does not rely on electricity to store information, but is driven by mechanical parts and is faster than the CPU It seems much slower.
Floppy disk: Floppy disk uses a soft polyester material to make the prototype negative, coated with magnetic material on both surfaces. Commonly used floppy disks have a diameter of 3.5 inches and a storage capacity of 1.44MB. Floppy disks read data through a floppy disk drive.
U disk: U disk is also called "flash disk" and can store data through the USB port of the computer. Compared with floppy disks, U disks have replaced floppy disks due to their small size, large storage capacity, and ease of portability.
Hard disk: The hard disk is composed of an aluminum alloy original plate coated with magnetic material. Each hard disk is composed of several magnetic discs.
Tape storage: Tape is also called sequential access memory SAM. It has a large storage capacity, but the search speed is very slow, and is generally only used as a data back-up store. There are three types of tape drives used in computer systems: reel tape drives, data streaming tape drives, and spiral scan tape drives.
Optical disc storage: Optical disc refers to a disc that uses optical means to store information. It applies optical storage technology, which uses lasers to write information on a certain medium, and then uses lasers to read out the information. Optical disk storage can be divided into: CD-ROM, CD-R, CD-RW, and DVD-ROM, etc.
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