,机电技术专业英语,2,Lesson Twelve,Text,Before we present the basis of CAD, it is appropriate to give a brief history. CAD is a product of the computer era. It originated from early computer graphic systems to the development of interactive computer graphics. Two such systems include the Sage Project at the Massachusetts Institute of Technology (MIT) and Sketchpad. The Sage Project was aimed at developing CRT displays and operating systems. Sketchpad was developed under the Sage Project. A CRT displays and light pen input were used to interact with the system. This coincidentally happened at about the same time that NC and APT (Automatically Programmed Tool) first appeared. Later, XY plotters were used as the standard hardcopy output device for computer graphics. An interesting note is that an XY plotter has the same basic structure as an NC drilling machine except that a pen is substituted for the tool on NC spindle.,CAD and Applications,Lesson Twelve,New Words and Expressions,Lesson Twelve,Lesson Twelve,Notes,1. MIT （Massachusetts Institute of Technology）马萨诸塞理工学院 2. Sage project Sage 系统 3. This coincidentally happened at about the same time that NC and APT （Automatically Programmed Tool）first appeared. CAD与初次出现的NC和APT（自动编程工具）碰巧同时问世。 Coincidentally 为插入语，at about the same time 为介词短语，可译为“几乎同时”。 4. An interesting note is that an XY plotter has the same basic structure as an NC drilling machine except that a pen is substituted for the tool on NC spindle. 一个有趣的现象是，除了绘图笔被NC机床上的主轴刀具替代之外，XY 绘图仪与NC钻床具有相同的基本结构。 the sameas “与相同”，as 为介词，引导短语。,Lesson Twelve,Lesson Twelve,参考译文,在讲述CAD的基本原理之前，先说说它的简史。CAD是计算机时代的产物。它从早期的计算机绘图系统发展到现在的交互式计算机图形学。两个这样的系统包括麻省理工学院的Sage Project及Sketchpad。Sage Project 旨在开发CRT显示器及操作系统。Sketchpad 是在Sage Project 下发展起来的。CRT显示和光笔输入用于与系统进行交互操作。CAD与初次出现的NC和APT（自动编程工具）碰巧同时问世。后来，X-Y绘图仪作为计算机绘图的标准拷贝输出装置使用。一个有趣的现象是X-Y绘图仪与NC钻床具有相同的基本结构，除了绘图仪被NC机床上主轴的刀具替代以外。,计算机辅助设计及其应用,谢谢观赏,www.sciencep.com,Thank You !,