Flash Drive, Keyboard - Computer Science and Information Technology

Flash Drive

Flash Drive is a portable storage medium consisting of a flash ROM, a special controller and an interface USB (Figure 3.16). Flash ROM is a non-volatile memory type that allows you to write and store data in microchips placed in a miniature flat casing. Flash memory cards do not have moving parts in their composition, which ensures high data safety when used in mobile devices (laptops, digital cameras, etc.). To read or write information, the flash drive is connected to the computer via the USB - port.

Devices are supported by Windows operating systems without the need to install any special drivers. When the device is turned on, it is automatically recognized by the system and registered. When shutting down, you must disconnect the device, after which it can be removed.

The main advantages of a flash drive: fast access, high reliability, compactness, durability and mobility.

The memory capacity of typical flash drives is from 2 to 32 GB, the speed of reading and writing is about 8 MB/s, the service life is 10 years. Memory cards used in mobile devices, photos and video cameras can have volumes of several GB. Their communication with the computer is done using a card reader connected

Fig. 3.16. Flash Drive

to the USB input. Many laptops and netbooks have separate connectors-inputs for direct connection of some types of memory cards.

A device that contains keys arranged in a specific order for entering characters and commands into the computer. The principle of operation of the keyboard is based on the fact that the mechanical pressing of the key is registered by the keyboard controller and transmitted as a code (single-byte word, key identification number) to the interface chip installed on the system board. At the same time, a hardware interrupt is initialized, which is serviced by the program stored in the BIOS. The processing program places the character code in the keyboard buffer, from where the application selects it and places it in the video buffer of the PC.

The location of the keys on the keyboard corresponds to accepted standards. The keyboard distinguishes between zones: alphanumeric keys, function keys, cursor keys and a numeric keypad (Figure 3.17).

After pressing the key, the controller in the keyboard body sends the code of the character of the pressed key to the system unit. The processor converts the transmitted code of a letter or command depending on the value of the language indicator (En or Ru ) and taking into account the behavior of the Shift, Caps Lock clicked them or not) displays a lowercase or uppercase letter on the monitor or executes the entered command.


Keyboard Layout

Fig. 3.17. Keyboard Layout

The standard keyboard is 101-key, in the last time - 107-key. The so-called ergonomic keyboard has an easy-to-use form, non-parallel and expanded; rows of keys for the left and right hands, palm rest, a special arrangement and shape of the keys, which relieves the user's hands during prolonged operation. The speed dial keyboard has a special layout of letters to reduce the movement of fingers.

Alphanumeric keys. The keys of this zone are used to enter letters, numbers, punctuation marks and symbols - as on the keyboard of the typewriter.

The distribution of alphabet and punctuation on the keys is called keyboard layout, depends on the language and takes into account the frequency of the sign in the language. On the key, the symbol of the English layout is written on top, and the United States layout is shown in red at the bottom. A key that prints characters in English mode? and /, in United States mode Windows usually prints a period, and together with the Shift key, a comma. In the operating systems DOS and Macintosh the layout of United States punctuation marks on the keys differs from Windows. The keyboard layout can be switched from English to United States and vice versa by using the Ctrl, Alt + Shift keys.

If the key is held down, its sign is automatically repeated on the screen. The keyboard can be adjusted: change the symbol repetition rate when the key is held down, change the delay time before starting the transition to the code repetition mode (used for disabled people that hold the key