Data and instructions must enter the data processing system, and information must leave it. These operations are performed by input and output (I/O) units that link the computer to its external environment.
The I/O environment may be human-related or human-independent.
A remote banking terminal is an example of a human-related input environment,
and a printer is an example of a device that produces output in
a human-readable format. An example of a human-independent input environment
is a device that measures traffic flow. A reel of magnetic tape upon which the collected data are stored in binary format is an example of a human-independent output.
Data enter input units in forms that depend uponthe particular device used. For example, data are entered from a keyboard in a manner similar to typing, and this differs from the way that data are entered by a bar-code scanner. However, regardless of the forms in which they receive their inputs, all input devices must provide a computer with data that are transformed into the binary codes that the primary memory of the computer is designed to accept. This transformation is accomplished by units called I/O interfaces. Input interfaces are designed to match the unique physical or electrical characteristics of input devices to the requirements of the computer system. Similarly, when output is available, output interfaces must be designed to reverse the process and to adapt the output to the external environment. These I/O interfaces are also called channels or input-output processors (IOP).
The major differences between devices are the media that they use and the speed with which they are able to transfer data to or from primary storage.
Input-output device speed. Input-output devices can be classified as high-speed, medium-speed, and low-speed. The devices are grouped according to their speed. It should be noted that the high-speed devices are entirely electronic in their operation or magnetic media that can be moved at high speed. Those high-speed devices are both input and output devices and are used as secondary storage. The low-speed devices are those with complex mechanical motion or operate at the speed of a human operator. The medium-speed devices are those that fall between — they tend to have mechanical moving parts which are more complex than the high-speed devices but not as complex as the low-speed.
High-speed devices: magnetic disk; magnetic tape.
Medium-speed devices: card readers; line printers; page printers; computer output microfilms; magnetic diskette; optical character readers; optical mark readers; visual displays.
Low-speed devices: bar-code readers; character printers; digitizers; keyboard
input devices; plotters; voice recognition and response units.
3. Дайте ответы на следующие во
1 When does the journey start?
2 Where is the museum situated ?
3 How can I get a membership card?
4 Do you provide a free delivery service?
5 How many exhibitions do you have?
6 Is it possible to buy tickets online?
7 How much does the ticket cost ?
8 What prices do you have for young people?
9 What is the size of the group?
10 Can I have a party in your cafe?
11 How can I get to the cafe by transport?
12 How many guests is it possible to invite?
13 Is there TV in hotel rooms?
14 How many visitors do you have per day?
15 What is the most popular bookshop?
Объяснение:
Travelling is the most exciting thing in the world. First of all, it lets us discover the world and to see different countries, experience their cultures and traditions. Moreover, we enrich our knowledge about life in general and particularly about ourselves. Travelling also gives us an opportunity to meet new interesting people, learn new languages and develop our skills. That’s why I’m trying to travel as much as possible.The best trip I’ve ever had in my life was to France. Although it happened two years ago, but I still recall this wonderful time with a great pleasure. I went there with two of my friends and it was really the right decision, because we travelled by coach and the journey took a long time. We were playing cards on the way, singing songs and joking all the time. As we arrived we checked in a hotel not far from the center. We were exhausted but in a good mood.The first day in Paris was fantastic. It was a bus tour around the city called Open Tour. We got on a bus at the nearest stop. It was amazing that it stopped in front of all sights, so we could get off and walk around the most famous places. We took thousands of photos of Eiffel Tower, the Louvre, Arch of Triumph and other monuments. We were impressed by the number of tourists and the beauty of the places we visited. We spent 4 other days in Paris, but this first time our impressions were thrilling.The next days we visited plenty of museums and had some time for small shopping to buy souvenirs. Last evening we went on a small excursion by boat. It was amazing to be on board and to see all the sights again as if they were saying goodbye to us.
Thus, it was fantastic time and I hope to come back to Paris one day to get the same marvelous emotions there.