北师大初中英语九年级（全一册）--Expansion4
时间：2018-12-29 作者：英语课 分类：北师大版初中英语九年级（全一册）
[00:00.74]Unit 4 Inventions and Inventors
[00:04.53]Expansion 4
[00:09.77]Exercise 1
[00:12.06]Have you ever asked yourself
[00:14.11]why the letters on your computer keyboard
[00:16.62]are placed in this strange way?
[00:19.42]Why are the keys not ordered
[00:21.27]according to the order of letters?
[00:24.22]To explain this ,
[00:25.71]we have to go back to the invention
[00:27.30]of the typewriter,
[00:29.31]Keyboards on the earliest typewriters were
[00:32.06]made with the keys in the order of leters ,
[00:35.16]It was easy to find the letters,
[00:37.52]but this system had a big disadvantage.
[00:40.97]When a persom typed letters that
[00:42.85]are often found together in English words ,
[00:45.64]the keys often got stuck because these letters
[00:49.01]were so close to each other.
[00:51.54]Christopher Latham Sholes,
[00:53.43]one of the inventors of the typewriter,
[00:56.07]invented a new keyboard system
[00:57.74]to solve this problem.
[01:00.58]The first six leters on this new keyboard were
[01:03.55]Q,W,E,R,T.and Y.
[01:07.60]So the system is called the QWERTY system.
[01:11.15]Letters that often appear together
[01:13.24]in English words are placed far apart
[01:15.58]on the QWERTY Keyboard.
[01:17.49]Nearly all keyboards today use this system.
[01:21.29]Even though someone could invent a new ststem.
[01:24.32]everyone is so familiar with the QWERTY system
[01:27.18]now that it will probably never be changed.
[01:34.73]Exercise 2
[01:37.87]The Morse Code 1 is a simple communication system.
[01:42.01]In this system.
[01:43.05]Short dots(·) and longer dashes(-)are used to
[01:46.66]represent the letters.
[01:48.72]If you listen to the Morse Code,
[01:50.64]a dash 2 is three times as long as a dot.
[01:54.39]The Morse Code was developed in the 1830s
[01:57.23]by the American inventor,Samuel F.b. Morse.
[02:01.07]with help from other scientists.
[02:03.40]The Morse Code is rarely 3 used today
[02:05.60]because modern communication methods
[02:07.54]are easier and faster.
[02:09.48]However,it is sometimes used in emergencies.
[02:13.35]For examle,
[02:14.55]a person who is covered under a building
[02:16.48]after an earthquake can call for help
[02:19.21]using the Morse Code.
[02:20.94]The well-known message SOS can be easily
[02:23.98]remembered:dot-dot-dot,dash-dash-dash,
[02:28.51]dot-dot-dot.
[02:28.93]
- What's the code for Tianjin?天津的代号是多少？
- Remember to use postal code.勿忘使用邮政编码。