USB stick

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USB (Universal Serial Bus) is a PnP interface for communication between computers and peripherals over a four wire shielded cable serial communication. In addition to turn the device 'on hot' or until the computer is turned on. Standard currently has the third revision (1.0, 1.1, 2.0, 3.0) and supports speeds of the original 12 Mbps to the current 4.8 Gbps. Allows sequentially connecting the device to the device, up to 127 devices or devices connected to the USB HUB. It is primarily designed for devices that communicate with a computer at low speeds as the mouse, keyboard and joystick and various other accessories like a remote mouse for presentations and the like. All belong to the specified device HID (Human Interface Device) devices. The voltage level of communication is 5 V and the current limit which can not be exceeded is 500 mA, but the active HUB is designed for larger loads because it has its own power source. The cable must not be longer than 3 m for the lower speed of communication and 5 m for the newer standard with high speed communication. This connector is similar to the IEEE 1394 connector, also called 'FireWire' speeds up to 400 Mbps and 800 Mbps in the development version.

As is standard improved by developing an interface for other types of devices that require faster speeds as a printer, modem, scanner, network card, adapter for optional external drive or CD/DVD, digital cameras and camcorders, TV tuner, and others. But the most interesting part is a handy portable memory, based on Flash technology, the size of sticks or stick. The memory capacity is usually in the range from 128 MB to 64 GB.

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Figure* 3.3.21 Memory stick. ( + / - )  

This little wonder of technology fits in your pocket, it can be hung on a chain around his neck. With a little electronics plays MP3 files, images, serves as a voice recorder and doing who knows what else. It can even be used on newer motherboards as a BOOT device. From the author's experience the most convenient form for use as a narrower and longer, because the light is inserted into the USB port on the computer and it does not cover the adjacent port. Can withstand without damage more than 100'000 write cycle is enough for a couple of years until they are smaller in size or even larger in capacity or capability.

Should not be shutting down when inserting or removing the 'stick'. When you insert the Windows XP will automatically recognize the device (Windows 98 needs driver), and in the 'System Tray' icon set that is used during the extraction. Over the icon opens a window 'Safely remove hardware' and through it off and stick it out without fear from the USB port. Should respect this procedure because it can damage the 'file-system'. The memory stick can be formatted as a floppy disk if there is a disturbance in his tracks as exFAT format, or for the purpose of gain on the CD appropriate program support to be installed on the computer.

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To data stored in permanent memory accessed, whether they are stored directly as binary notation (stick) or a modulated signal to the binary (disc), there should be a mechanism that will with their logical abilities, they allow the user to be accessed in an acceptable way. The same requirement applies to write, delete, copy or move data. That's what worried FILE SYSTEM; physical structure that binary on the disc translates into a logical structure, such as directories-folders and files and perform their cataloging. Method and ease of presentation depends on the operating system, and the initial system when everything was working using the entered commands and commands (DOS, for example) are underway to move image using mouse (Windows XP for example) to the same effect. The same type of device does not use the same file system, nor can one default file system can be applied to all devices. File systems that are in use on are known as, FAT, NTFS, Ext2, Ext3, XFS, and others. The way that allows access to files and features some very different. Operating systems can essentially support one or more of the file system, which means that one of the disk partition can be prepared for one type and the other is for a different file system.

Permanent memory is of great importance in the DCS. No ugly events for the user from losing DCS painstakingly collected and analyzed data. While great attention is paid to the quality of the media making a memorable, are subject to breakdown and permanent damage. Therefore, institutions that use a lot of data using systems connected disks (RAID) or a CLUSTER of computers and also regularly (daily) are stored (archived) data from magnetic disks on a machine with a tape or floppy disk, either as:

            1.) Complete all data storage disc (FULL BACKUP).
            2.) Additional storage of only the changed data (INCREMENTAL).

Complete storage essentially occurs only the first time or as a monthly or yearly archives, kept separate from the current archive. CD-R is still not suitable for such an archive, the more so as it is not possible to perform a supplement store only the changed contents.

In order to protect the data integrity and each block of data at enrollment in the storage medium is assigned to control the sum of all the data blocks, or other information to verify - CRC data (Cyclical Redundancy Check). Data are naturally binary numbers and each reading block calculates and compares the sum of control inscribed with the block. In case of failure to perform a reading and alert the user if the sum is not correct.

Basically any kind of writing or communicating with the data contain some kind of RULES (PROTOCOLS) that allow that all those who use these rules can share data or as the tracks on the media or direct communication. These rules then become part of a generally accepted STANDARD that incorporates everything from how to write, tests to failure, communication, display on screen, layout of letters on the keyboard, and more.

Permanent memory device is certainly a significant part of DCS. But no matter how the system is used, important data should always be stored in multiple places, physically dislocated. Never be too careful. Although optical media is very popular certainly not a safe way of storing the data due to the high sensitivity to sunlight, which can kill them after a one-hour exposure to sunlight, and sensitivity to scratch the surface. Any media that is used for good is to have amplified the media data. How much data to fit the most popular media have the memory of the human brain showing the next table.

Comparison of media for data storage
Media Capacity (bytes) Page A4
Floppy 3.5" - DS/HD 1'440'000 B 288
CD-ROM 700'000'000 B 140'000
DVD-ROM - 4 layers 17'000'000'000 B 3'400'000
Hard Disk 200 GB 200'000'000'000 B 40'000'000
Human Brain 125'000'000'000'000 B 25'000'000'000

On one A4 page of text fit approximately 5'000 characters. The trouble for the human brain is that it can not be well 'address' that kind of data, and so far has neither effective methods of copying. Attention should be given to the statement at the end of Appendix 9i.


  Citing of this page:
Radic, Drago. " IT - Informatics Alphabet " Split-Croatia.
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