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 pressed).

The key area in the top row of the keyboard from F1 to F2, by pressing which a certain action is preprogrammed by the operating system or performed program. The F1 key is almost always help with the program.

The control keys send commands to a fixed destination.

Enter - input, the end of the command set and its parameters, the signal to proceed to its execution; when typing - an indication of the end of the paragraph and the transition to the next paragraph.

Esc (English Escape - escape) - canceling, sometimes interrupting the current operation, the preparing command (closing the command window, or dialog boxes, message boxes).

Print Screen - save a copy of the screen image in memory, then you can insert it as a photo into the window of another program.

Alt + Print Screen - save a copy of the active window of an open folder or program in memory, then you can paste it as a photo into the window of another program.

Pause (pause) - pause some programs until you press a key.

Keys for moving the cursor. Cursor - a place index in the program window or command window where you can enter text, a number, make corrections, insert an object. To move the cursor on the monitor screen on the keyboard there are four keys with arrows - right, left, up, down. The cursor is moved with the mouse pointer and keyboard keys. In combination with the Shift, Ctrl, Alt keys, they change their action depending on the downloaded program.

Shortcut keys:

Note (English - home) and End (English - end) - usually move the cursor to the beginning or end of a line of text or to the left upper (bottom right ) the angle of the screen;

Page Up and Page Down (English - screen down) - the scrolling keys of a large document or picture on the monitor screen


In the text editor of Word, the action of the Note, End, Page Up, Page Down keys can be modified when they are pressed together with the Ctrl key. In this case, the cursor will be translated accordingly into the beginning or the end of the document, one page of the document up or down. Pressing Ctrl together with the cursor keys to the left or right moves it to the beginning of the words in the document line.

Tab (English, tabulation - tab) - inserting a larger space (tabulation), in the table - moving the cursor to the next cell. In the dialog box of the command in the program, this key allows you to select the parameters for its execution. The combination of Shift + Tab moves to the previous cell in the table or to the previous parameter in the command window.

Keys for changing and deleting characters. Insert - the key for switching insert and replace mode in text programs. Insert - letters are inserted between existing letters (normal mode). Replacement - the letters are inserted on top available to the right of the letter cursor, eating them or the entire selected block of text.

Delete (English - delete) - the key for deleting the character at the cursor position, gradually eating shifting the right side of the line.

Backspace (English - space back) - delete left, move the cursor with the character to the left. The key is useful for removing errors during the dialing process.

The Delete and Backspace keys remove not only the symbol, but also a pre-selected object: a block of text, a picture, selected files in a folder window.

Indicators for turning on the keys on the keyboard. On the right side of the keyboard at the top is the dashboard: Num Lock (English Numeric Key Lock), Caps Lock Capital Letters Lock - the lock of capital letters), Scroll Lock (English - the lock of scrolling of the screen). The indicators turn on when you press the same auxiliary keys to visually fix the inclusion of the corresponding functions: the inclusion of the digits of the right numeric keypad, the lock of caps, the scroll lock of the screen in some programs.

Modifying keys and other keys mode. Three keys: Shift shift - shift, Ctrl (English, control - ), Alt (English alternate - alternative, i.e., choosing another option) - work like this: by holding this key, press some other one. These keys modify the action of an alphabetic, numeric, functional or moving key. In order to install additional keys on the keyboard, the action of the existing keys is changed, and the variation variant depends on which auxiliary key is pressed together with the main, semantic key.

The action depends on the program being run. If typing keys Shift, Ctrl, Alt are not pressed, then the keys give lowercase letters and numbers, and the keys of the right numeric keypad give what defines the Num Lock switch (if it is not enabled, they control the cursor).

If the Shift key is pressed, the keys give uppercase letters, and instead of the numbers, punctuation marks and symbols of type $, %. If you hold Shift in the pressed state, the keys of the right numeric keypad refuse what the Num Lock switch determines (even if it is on, they print not the digits, but move the cursor). For many programs and operations, the Shift key changes the action of the other key to the opposite.

Pressing the Caps Lock, key will enter uppercase letters. To make it clear that the capitalization is set, the key turns on the Caps Lock indicator. If Caps Lock is , does not print letters uppercase, and again lowercase letters. Caps Lock does not affect the pressing of the keys of the digital series: what will be printed, a number or punctuation, from Caps Lock does not depend, but is determined by the Shift

If you press the secondary key, nothing happens as a rule.

Warning: Do not try to hit the keys working together at the same time. First, press and hold the modifier key, then quietly press the semantic key. Only at the moment when the semantic key has joined, and the expected action or command will occur.

If the computer "hangs up." The Ctrl, Alt, Del, keys pressed together in Windows call the Task Manager window (shutdown programs) and are used if a program or the entire system does not obey any commands ("hang"). The computer's power does not turn off, but only the operating system in RAM is rebooted. If you see a program in the appeared list of downloaded applications and the program failed, and the "ncs responds" line, you must select the line of this program and press the Delete task button - unload and refuse the program execution. The Shutdown command allows you to crash the entire Windows operating system. Stretched the key combination is hard to press by accident, and it's important not to interrupt the work by mistake.

The right block of numeric keys. The keyboard contains the right key block from 0 to 9, which in addition to the numbers also contains a number of duplicate keys.

Num Lock - the key for switching the block of right-hand numeric keys from digital mode to cursor movement and vice versa. When the Num Lock indicator is not lit, the keys of the right numeric keypad duplicate the arrow keys, insert and delete keys. If the Num Lock key turns on the Num Lock indicator, the slave key block represents digits, even when combined with the Shift, Ctrlw keys with function keys. Right-handed numerical keys are used for fast professional set of number arrays, for example financial and statistical tables.

Right arithmetic keys [+], [-], [*], [/] - right plus, right minus, star multiplier and fraction the division sign - are used to enter symbols and arithmetic operations in mathematical programs. Some programs respond to these signs as parameters of their commands.

The right key Ins duplicates the action of the Insert, key and the action of the right key Del depends on the state of the Num Lock. So, if the indicator is off, then the key deletes the character; if enabled with the English keyboard layout turned on - puts a period, and when United States is on - puts a comma.

The Alt key and the number keys from the right-hand numeric keypad are used to enter characters by codes: they can enter characters that are not present on the keys. For example, Alt +0167 prints § if you enable Num Lock. The code of characters that can be entered by their codes is given by reference tables (so you can enter the characters present on the keys ). The character codes and keyboard shortcuts for entering them can be found in the Symbol Table, the shortcut for displaying which is on the screen is in the Start - Programs - Standard - System Tools. In Symbol Table , select the required character, and in the lower right corner of the window, a shortcut to display it in the text string is displayed. The Num Lock key switches on the right-hand numeric keypad, and the indicator lights. Hold down the left Alt button, key in the character code. Matching code-symbol for Cyrillic depends on the encoding of Windows, DOS, in Word - from the selected font. For example, the keys Alt + 0176 enter the symbol ° (degree), and the keys Alt + 0177 - ± (plus or minus).

The keyboard can have additional Windows shutdown keys, context menu, multimedia, Internet, mail, power saving.

Hotkeys. Hotkey - a key or a set of keys that execute certain commands in the operating system, in the active program or run programs. Typically, this is one of the & F12 softkeys, or the Ctrl, Shift, Alt keys, along with the F1 & divide; F12 keys, with alphabetic or other keys.

The distribution of commands to hot keys determines the configuration of the operating system and the program being launched. It is required that the actions of the hot keys of the operating system and the executable program do not contradict each other, otherwise the hot keys of the commands of the executable program win.

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