Removable storage media can include any device designed to transfer information from one computing device to another.
The most common removable media are:
- floppy disks (already rarely used);
- optical disks;
- flash memory devices;
- flash cards;
- removable hard drives.
Optical discs
These are flat circular discs on which binary data is recorded in the form of microscopic grooves called pits. The base is usually made of polycarbonate. In the upper part of the base is encoding material, which occupies the bulk of the disk and forms a special layer. Writing and reading information from the disc is carried out using a laser. In this case, the laser beam is directed to a special layer and is reflected from it, modulated by pits. The decoding of the reflected beam is carried out by the reader.
There are 3 types of optical discs:
- only for reading;
- for single recording only;
- for multiple recording.
In recorded removable storage media between the base and the reflective layer is an organic dye. In recordable discs, the intermediate layer consists of a material with a variable phase state.
The advantage of optical discs is the ability to store information for a long time. But they are very susceptible to damage during their constant use.
Flash memory
It is an electronic non-volatile medium, information from which can be erased and reprogrammed. Removable storage media store information in a plurality of memory cells based on floating gate transistors. In devices on single-level cells, each stores 1 bit of information. In devices on multi-level cells, one can store more than 1 bit of data.
Each flash cell is a normal MOS transistor. With one small nuance - this transistor has 2 gates, not one. The memory cell can be considered as a normal electric switch, in which current flows between two contacts, the role of which is played by the source and drain. The current flow is controlled by a floating shutter and a control shutter.
Flash specifications
For any user, one of the main parameters of a flash drive will be its capacity. The higher its value, the more information it can contain. Of great importance are parameters such as read speed and write speed of information on removable media. Reading data is much faster than writing it.
Disadvantages of flash memory:
- Limited resource. When a flash drive is charged, its structure changes. As a result, the number of cycles of writing / reading information is sharply limited. As a rule, it varies from several thousand to hundreds of thousands of times.
- Limited period of information storage. Manufacturers give a guarantee on modern information media of this type for an average of 5 years. The actual storage life of a transistor charge is 10–20 years.
Flash cards
Flash cards include electronic devices designed to store digital information. These devices are mainly used in digital cameras, mobile phones, laptops, tablets, portable media players, video game consoles, synthesizers, electronic keyboards and digital pianos.
The main parameters of the media include the capacity and speed of writing / reading data. Card readers are used to connect these devices to a computer, which, in turn, can also be removable or internal. Removable card readers connect to a PC via a USB interface.
The camera’s flash card can be connected to a PC without removing it from the camera. To do this, you need a special cable for connection via the USB port.
external HDs
A type of hard disk drive enclosed in a plastic or metal case, so that it can be used similarly to flash memory.
Removable storage media can be connected to a computer in the following ways:
- via USB port;
- using the Fire Wire bus;
- via eSATA interface;
- wirelessly.
Advantages of external hard drives:
- portability like a flash drive;
- higher capacity compared to a standard hard drive. An external 1tb hard drive - these days you will not surprise anyone with a device with such a capacity.
Comparison of external hard drives with internal
Internal hard drives are connected directly to the motherboard, while external ones are connected to the USB port of the computer, which provides a connection to the motherboard.
Operating systems and software are mainly installed on internal drives, while external ones are used to store photos, videos and various files. But the design of external drives is the same as that of internal drives. In general, an external hard drive can be installed in a laptop or personal computer without making design changes.
Power to internal media comes directly from the power supply located inside the system unit of the computer. Removable storage media are powered either through a data cable, or have their own wire for connecting to a power source.
External hard drives are much more likely to move from one place to another compared to internal ones. As a result, the risk of mechanical damage to these discs increases.