External memory

Hard drive. Hard disk drives (hard drives) are designed for permanent storage of information used when working with a computer: operating system programs, frequently used software packages, document editors, etc. (Fig. 6).

Disk capacity.For the user, hard disk drives differ from each other primarily in their capacity, i.e., how much information is placed on the disk. Now computers are mostly equipped with hard drives of 80 GB or more.

The speed of the disk.The speed of the disk is characterized by two indicators:

  • The time of access to data on the disk.
  • The speed of reading and writing data to disk.

These characteristics relate to each other in approximately the same way as the acceleration time and the maximum speed of the car. When reading or writing short blocks of data located in different parts of the disk, the speed of operation is determined by the time of access to data – just as when driving a car around the city during rush hour with constant acceleration and braking, the maximum speed developed by the car is not so important. But when reading or writing data (tens or hundreds of kilobytes) of files, the bandwidth of the exchange path with the disk is much more important – just as when driving a car on a highway, the speed of the car is more important than the acceleration time.

Floppy disk drives (floppy disks, floppy disks) allow you to transfer documents from one computer to another, store information. The main disadvantage of the drive is its small capacity (only 1.44 MB) and unreliability of information storage. However, this method is the only way for many Russian users to transfer information to another computer. On computers of the last years of release, 3.5-inch (89mm) floppy disk drives are installed. Previously, 5.25-inch drives were used. They, despite their size, have a smaller capacity and are less reliable and durable. Both types of floppy disks have write protection (a jumper on the protective case of the floppy disk). Floppy disks belong to information storage devices (Fig. 7).

A CD-ROM reader (CD-ROM) is designed to read CD-ROM recordings.

The advantages of the device are large disk capacity, fast access, reliability, versatility, low cost. The main concept characterizing the operation of this device is speed. The main disadvantage of standard CD-ROM drives is the inability to record information. Other devices are needed for this:

CD-R–disc, with the ability to record information once, in Russia they are called “blanks”. Recording to these discs is carried out due to the presence of a special photosensitive layer on them, which burns out under the influence of a high-temperature laser beam.

CD-RW– disc, with the possibility of multiple recording of information.

Recently, a DVD-ROM device designed for reading DVD format discs has become increasingly widespread.


Learn More →