What is external memory?
External memory should be understood as a kind of personal computer memory that is implemented with the help of various external equipment, capable of storing a large amount of information for a long time. The external storage device is compared with the internal memory of a computer, for example, random access memory device has a large volume, but low data rate.
Features and external memory devices
Today, there are many external storage devices. In relation to a personal computer, they can be: hard drives (external and internal), storage on floppy disks, which are designed exclusively for reading and writing, laser disks, tape drives, flash cards etc. All of these devices are separated by type of access to information. These can be direct access or sequential access. They are separated by the fact that in devices of the direct access / transfer of information does not depend on its location on the media, and in sequential access devices such dependence exists. The amount of memory on the hard drives (both external and internal) can reach several terabytes. The capacity for flexible magnetic discs is usually not larger than 1.44 MB (now hardly used). CD drives have a capacity of 640 MB, and a DVD with a capacity of up to 17 gigabytes. The maximum amount of USB storage devices now up to 64 GB.
With regard to the main characteristics of external memory, that is their information capacity, performance, data reliability, and cost. The storage capacity should understand the maximum amount of information that can be written to the device. It should be noted that, as a rule, it is much more than the capacity of the internal memory. Unfortunately, the speed or the performance of such devices is many times inferior to the devices internal memory. It is determined by the access time of the recording and reading of information stored on the device. As for reliability, this option is almost identical to the internal memory. Reliability may be affected only in case of incorrect or careless use of devices of external memory, and in the presence of various malicious software.