Что такое input output

Input and Output Devices

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Before a computer can process your data, you need some method to input the data into the machine. The device you use will depend on what form this data takes (be it text, sound, artwork, etc.).

Similarly, after the computer has processed your data, you often need to produce output of the results. This output could be a display on the computer screen, hardcopy on printed pages, or even the audio playback of music you composed on the computer.

The terms “input” and “output” are used both as verbs to describe the process of entering or displaying the data, and as nouns referring to the data itself entered into or displayed by the computer.

Below we discuss the variety of peripheral devices used for computer input and output.

Input Devices

Keyboard

The computer keyboard is used to enter text information into the computer, as when you type the contents of a report. The keyboard can also be used to type commands directing the computer to perform certain actions. Commands are typically chosen from an on-screen menu using a mouse, but there are often keyboard shortcuts for giving these same commands.

In addition to the keys of the main keyboard (used for typing text), keyboards usually also have a numeric keypad (for entering numerical data efficiently), a bank of editing keys (used in text editing operations), and a row of function keys along the top (to easily invoke certain program functions). Laptop computers, which don’t have room for large keyboards, often include a “fn” key so that other keys can perform double duty (such as having a numeric keypad function embedded within the main keyboard keys).

Improper use or positioning of a keyboard can lead to repetitive-stress injuries. Some ergonomic keyboards are designed with angled arrangements of keys and with built-in wrist rests that can minimize your risk of RSIs.

Most keyboards attach to the PC via a PS/2 connector or USB port (newer). Older Macintosh computers used an ABD connector, but for several years now all Mac keyboards have connected using USB.

Pointing Devices

The graphical user interfaces (GUIs) in use today require some kind of device for positioning the on-screen cursor. Typical pointing devices are: mouse, trackball, touch pad, trackpoint, graphics tablet, joystick, and touch screen.

Pointing devices, such as a mouse, connected to the PC via a serial ports (old), PS/2 mouse port (newer), or USB port (newest). Older Macs used ADB to connect their mice, but all recent Macs use USB (usually to a USB port right on the USB keyboard).

Mouse

PC Keyboard (you have one in front of you that you can see for a closer look)

The mouse pointing device sits on your work surface and is moved with your hand. In older mice, a ball in the bottom of the mouse rolls on the surface as you move the mouse, and internal rollers sense the ball movement and transmit the information to the computer via the cord of the mouse.

The newer optical mouse does not use a rolling ball, but instead uses a light and a small optical sensor to detect the motion of the mouse by tracking a tiny image of the desk surface. Optical mice avoid the problem of a dirty mouse ball, which causes regular mice to roll unsmoothly if the mouse ball and internal rollers are not cleaned frequently.

A cordless or wireless mouse communicates with the computer via radio waves (often using BlueTooth hardware and protocol) so that a cord is not needed (but such mice need internal batteries).

A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the GUI. The traditional PC mouse has two buttons, while the traditional Macintosh mouse has one button. On either type of computer you can also use mice with three or more buttons and a small scroll wheel (which can also usually be clicked like a button).

Touch pad

Two-button mouse with scroll wheel

Wireless Macintosh mouse

Most laptop computers today have a touch pad pointing device. You move the on-screen cursor by sliding your finger along the surface of the touch pad. The buttons are located below the pad, but most touch pads allow you to perform “mouse clicks” by tapping on the pad itself.

Touch pads have the advantage over mice that they take up much less room to use. They have the advantage over trackballs (which were used on early laptops) that there are no moving parts to get dirty and result in jumpy cursor control.

Trackpoint

Touch pad of a PC laptop

Trackball

The trackball is sort of like an upside-down mouse, with the ball located on top. You use your fingers to roll the trackball, and internal rollers (similar to what’s inside a mouse) sense the motion which is transmitted to the computer. Trackballs have the advantage over mice in that the body of the trackball remains stationary on your desk, so you don’t need as much room to use the trackball. Early laptop computers often used trackballs (before superior touch pads came along).

Trackballs have traditionally had the same problem as mice: dirty rollers can make their cursor control jumpy and unsmooth. But there are modern optical trackballs that don’t have this problem because their designs eliminate the rollers.

Joysticks

Joysticks and other game controllers can also be connected to a computer as pointing devices. They are generally used for playing games, and not for controlling the on-screen cursor in productivity software.

Touch screen

Some computers, especially small hand-held PDAs, have touch sensitive display screens. The user can make choices and press button images on the screen. You often use a stylus, which you hold like a pen, to “write” on the surface of a small touch screen.

Graphics tablet

A graphics tablet consists of an electronic writing area and a special “pen” that works with it. Graphics tablets allows artists to create graphical images with motions and actions similar to using more traditional drawing tools. The pen of the graphics tablet is pressure sensitive, so pressing harder or softer can result in brush strokes of different width (in an appropriate graphics program).

Scanners

A scanner is a device that images a printed page or graphic by digitizing it, producing an image made of tiny pixels of different brightness and color values which are represented numerically and sent to the computer. Scanners scan graphics, but they can also scan pages of text which are then run through OCR (Optical Character Recognition) software that identifies the individual letter shapes and creates a text file of the page’s contents.

Microphone

A microphone can be attached to a computer to record sound (usually through a sound card input or circuitry built into the motherboard). The sound is digitized—turned into numbers that represent the original analog sound waves—and stored in the computer to later processing and playback.

MIDI Devices

MIDI ( Musical Instrument Digital Interface ) is a system designed to transmit information between electronic musical instruments. A MIDI musical keyboard can be attached to a computer and allow a performer to play music that is captured by the computer system as a sequence of notes with the associated timing (instead of recording digitized sound waves).

Output Devices

CRT Monitor

The traditional output device of a personal computer has been the CRT (Cathode Ray Tube) monitor. Just like a television set (an older one, anyway) the CRT monitor contains a large cathode ray tube that uses an electron beam of varying strength to “paint” a picture onto the color phosphorescent dots on the inside of the screen. CRT monitors are heavy and use more electrical power than flat panel displays, but they are preferred by some graphic artists for their accurate color rendition, and preferred by some gamers for faster response to rapidly changing graphics.

Flat Panel Monitor

A flat panel display usually uses an LCD ( Liquid Crystal Display ) screen to display output from the computer. The LCD consists of several thin layers that polarize the light passing through them. The polarization of one layer, containing long thin molecules called liquid crystals, can be controlled electronically at each pixel, blocking varying amounts of the light to make a pixel lighter or darker. Other types of flat panel technology exist (such as plasma displays) but LCDs are most commonly used in computers, especially laptops.

Older LCDs had slow response times and low contrast, but active matrix LCD screens have a transparent thin film transistor ( TFT ) controlling each pixel, so response, contrast, and viewing angle are much improved.

Flat panel displays are much lighter and less bulky than CRT monitors, and they consume much less power. They have been more expensive than CRTs in the past, but the price gap is narrowing. You will see many more flat panels in the future.

As with CRTs, the display size of a flat panel is expressed in inches, and the resolution is the number of pixels horizontally and vertically on the display.

Ink Jet Printer

Flat panel display (LCD)

For hardcopy (printed) output, you need some kind of printer attached to your computer (or available over a network). The most common type of printer for home systems is the color ink jet printer. These printers form the image on the page by spraying tiny droplets of ink from the print head. The printer needs several colors of ink (cyan, yellow, magenta, and black) to make color images. Some photo-quality ink jet printers have more colors of ink.

Ink jet printers are inexpensive, but the cost of consumables (ink cartridges and special paper) make them costly to operate in the long run for many purposes.

Laser Printer

A laser printer produces good quality images by the same technology that photocopiers use. A drum coated with photosensitive material is charged, then an image is written onto it by a laser (or LEDs) which makes those areas lose the charge. The drum then rolls through toner (tiny plastic particles of pigment) that are attracted to the charged areas of the drum. The toner is then deposited onto the paper, and then fused into the paper with heat.

Most laser printers are monochrome (one color only, usually black), but more expensive laser printers with multiple color toner cartridges can produce color output.

Laser printers are faster than ink jet printers. Their speed is rated in pages per minute ( ppm ). Laser printers are more expensive than ink jets, but they are cheaper to run in the long term if you just need good quality black & white pages.

Other Printers

Multi-function printers are available that not only operate as a computer printer, but also include the hardware needed to be a scanner, photocopier, and FAX machine as well.

Dot matrix printers use small electromagnetically activated pins in the print head, and an inked ribbon, to produce images by impact. These printers are slow and noisy, and are not commonly used for personal computers anymore (but they can print multi-layer forms, which neither ink jet or laser printers can).

Sound Output

Computers also produce sound output, ranging from simple beeps alerting the user, to impressive game sound effects, to concert quality music. The circuitry to produce sound may be included on the motherboard, but high quality audio output from a PC usually requires a sound card in one of the expansion slots, connected to a set of good quality external speakers or headphones.

Multimedia is a term describing computer output that includes sound, text, graphics, movies, and animation. A sound card is an example of a multimedia output device (as is a monitor that can display graphics).

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Input and Output Devices

An input/output device, often known as an IO device, is any hardware that allows a human operator or other systems to interface with a computer. Input/output devices, as the name implies, are capable of delivering data (output) to and receiving data from a computer (input).
An input/output (I/O) device is a piece of hardware that can take, output, or process data. It receives data as input and provides it to a computer, as well as sends computer data to storage media as a storage output.

There are many IO Devices available, some of them are:

Input Devices

Keyboard

The keyboard is the most frequent and widely used input device for entering data into a computer. Although there are some additional keys for performing other operations, the keyboard layout is similar to that of a typical typewriter.
Generally, keyboards come in two sizes: 84 keys or 101/102 keys, but currently keyboards with 104 keys or 108 keys are also available for Windows and the Internet.

Mouse

The most common pointing device is the mouse. The mouse is used to move a little cursor across the screen while clicking and dragging. The cursor will stop if you let go of the mouse. The computer is dependent on you to move the mouse; it won’t move by itself. As a result, it’s an input device.
A mouse is an input device that lets you move the mouse on a flat surface to control the coordinates and movement of the on-screen cursor/pointer.
The left mouse button can be used to select or move items, while the right mouse button when clicked displays extra menus.

Joystick

A joystick is a pointing device that is used to move the cursor on a computer screen. A spherical ball is attached to both the bottom and top ends of the stick. In a socket, the lower spherical ball slides. You can move the joystick in all four directions.

The joystick’s function is comparable to that of a mouse. It is primarily used in CAD (Computer-Aided Design) and playing video games on the computer.

Light Pen

A light pen is a type of pointing device that looks like a pen. It can be used to select a menu item or to draw on the monitor screen. A photocell and an optical system are enclosed in a tiny tube.
When the tip of a light pen is moved across a monitor screen while the pen button is pushed, the photocell sensor element identifies the screen location and provides a signal to the CPU.

Scanner

A scanner is an input device that functions similarly to a photocopier. It’s employed when there’s information on paper that needs to be transferred to the computer’s hard disc for subsequent manipulation.
Scanner collects images from the source and converts them to a digital format that may be saved on a disc. Before they are printed, these images can be modified.

OCR

OCR stands for optical character recognition, and it is a device that reads printed text. OCR optically scans the text, character by character, turns it into a machine-readable code, and saves it to the system memory.

Bar Code Reader

A bar code reader is a device that reads data that is bar-coded (data that is represented by light and dark lines).
Bar-coded data is commonly used to mark things, number books, and so on. It could be a handheld scanner or part of a stationary scanner.
A bar code reader scans a bar code image, converts it to an alphanumeric value, and then sends it to the computer to which it is connected.

Web Camera

Because it records a video image of the scene in front of it, a webcam is an input device. It is either built inside the computer (for example, a laptop) or attached through a USB connection.
A webcam is a computer-connected tiny digital video camera. It’s also known as a web camera because it can take images and record video. These cameras come with software that must be installed on the computer in order to broadcast video in real-time over the Internet. It can shoot images and HD videos, however, the video quality isn’t as good as other cameras (In Mobiles or other devices or normal cameras).

Output Devices

Monitor

Monitors, also known as Visual Display Units (VDUs), are a computer’s primary output device. It creates images by arranging small dots, known as pixels, in a rectangular pattern. The amount of pixels determines the image’s sharpness.
The two kinds of viewing screen used for monitors are:
(1) Cathode-Ray Tube (CRT): Pixels are minuscule visual elements that make up a CRT display. The higher the image quality or resolution, the smaller the pixels.
(2) Flat-Panel Display Cathode-Ray Tube Monitor: In comparison to the CRT, a flat-panel display is a type of video display with less volume, weight, and power consumption. They can be hung on the wall or worn on the wrist.
Flat-panel displays are currently used in calculators, video games, monitors, laptop computers, and graphical displays.

Printer

Printers are output devices that allow you to print information on paper.

There are two types of printers:

(a) Impact Printer:

(b) Non-Impact Printers:

Sample Questions

Question 1. List Disadvantages of CRT Monitor.

Answer:

Question 2. Compare input & Output Devices.

Answer.

Question 3. What are the types of flat-panel displays?

Answer:

There are 2 types of flat-panel displays :
(a) Emissive Display: Devices that turn electrical energy into light are known as emissive displays. Example: LEDs, Plasma panels, thin film electroluminescent displays etc.
(b) Non- Emissive Display: Optical effects are used in Non-Emissive displays to turn sunshine or light from another source into graphical patterns. LCDs are a good example (Liquid Crystal Device).

Question 4. Explain the output device: Plotter.

Answer:

A plotter is a device that prints graphics in a variety of color formats with high-quality images. It’s similar to a printer, but with more advanced capabilities.
Plotter allows us to create pictures, 3D postcards, advertising signs, charts, and various designs of the internal structure of building machines, as well as print large maps, architectural drawings, large-format printing, and create pictures, 3D postcards, advertising signs, charts, and various designs of the internal structure of building machines.

Question 5. Compare Impact & Non-Impact Printers.

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Angular. Понимание @Input, @Output и EventEmitter

Привет, Хабр! Представляю вашему вниманию перевод статьи «Understanding @Input, @Output and EventEmitter in Angular» автора foolishneo.

Приветствую всех желающих накапливать информацию о тонкостях работы фреймворка Angular.

Сегодня посчитал нужным лучше изучить информацию, касающуюся организации взаимодействия между компонентами Angular и начать практиковать переводы интересующих меня статей с английского.

Надеюсь найдутся те, для кого перевод статьи с Medium будет полезен.

Давно имея желание начать переводить полезные статьи с английского, решил начать с простенькой, весьма не объемной, но возможно, дополняющей имеющиеся знания статейки. К Вашему вниманию, господа…

Для тех, кто новенький в изучении Angular, декораторы Input и Output могут вызывать смущение, особенно, когда Вы пытаетесь разобраться в их назначении с помощью примеров кода. В этой статье, я попытаюсь объяснить их максимально простым способом.

Инструмент для обмена данными

В первую очередь, задача декораторов Input и Output состоит в обмене данными между компонентами. Они являются механизмом для получения/отправки данных от одного компонента к другому.

Input используется для получения данных, в то время как Output для их отправки. Output отправляет данные выставляя их в качестве производителей событий, обычно как объекты класса EventEmitter.

Таким образом, когда Вы видите код, на подобии этого:

@Input и Output в действии.

Обратите внимание на пример.

Здесь я создал 2 компонента, компонент hello, вложенный в компонент app. Компонент hello имеет Input и Output:

Компонент hello ожидает получить значение типа «строка» и поместить его в качестве значения свойства myFriend.

Каждый раз, когда Вы кликните на него, свойство отправки данных onClick декоратора Output передаст «внешнему миру» строку с содержанием «Neo».

Ниже расположен код компонента app:

Обратите внимание что компонент app использует тег компонента hello в своем шаблоне, который совершает 2 действия:

Вы можете увидеть приложение в действии здесь.

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