北师大初中英语九年级Expansion 4（MP3+LRC）

[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 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 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 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]