目录TOC\o"1-3"\h\z\uHYPERLINK\l"_Toc188800989"第三章分支语句和编程设计PAGEREF_Toc188800989\h1HYPERLINK\l"_Toc188800990"3.1自上而下的编程方法简介PAGEREF_Toc188800990\h1HYPERLINK\l"_Toc188800991"3.3关系运算符和逻辑运算符PAGEREF_Toc188800991\h4HYPERLINK\l"_Toc188800992"3.3.1关系运算符PAGEREF_Toc188800992\h4HYPERLINK\l"_Toc188800993"3.3.2小心==和~=运算符PAGEREF_Toc188800993\h5HYPERLINK\l"_Toc188800994"3.3.3逻辑运算符PAGEREF_Toc188800994\h6HYPERLINK\l"_Toc188800995"例3.1PAGEREF_Toc188800995\h7HYPERLINK\l"_Toc188800996"3.3.4逻辑函数PAGEREF_Toc188800996\h7HYPERLINK\l"_Toc188800997"测试3.1PAGEREF_Toc188800997\h7HYPERLINK\l"_Toc188800998"3.4选择结构(分支语句)PAGEREF_Toc188800998\h8HYPERLINK\l"_Toc188800999"3.4.1if结构PAGEREF_Toc188800999\h8HYPERLINK\l"_Toc188801000"3.4.2if结构举例PAGEREF_Toc188801000\h9HYPERLINK\l"_Toc188801001"例3.2PAGEREF_Toc188801001\h9HYPERLINK\l"_Toc188801002"例3.3PAGEREF_Toc188801002\h12HYPERLINK\l"_Toc188801003"3.4.3关于if结构使用的注意事项PAGEREF_Toc188801003\h13HYPERLINK\l"_Toc188801004"例3.4PAGEREF_Toc188801004\h14HYPERLINK\l"_Toc188801005"3.4.4switch结构PAGEREF_Toc188801005\h15HYPERLINK\l"_Toc188801006"3.4.5try/catch结构的应用PAGEREF_Toc188801006\h16HYPERLINK\l"_Toc188801007"测试3.2PAGEREF_Toc188801007\h17HYPERLINK\l"_Toc188801008"3.5附加的画图特性PAGEREF_Toc188801008\h17HYPERLINK\l"_Toc188801009"3.5.1控制x，y轴绘图的上下限PAGEREF_Toc188801009\h18HYPERLINK\l"_Toc188801010"3.5.2在同一坐标系内画出多个图象PAGEREF_Toc188801010\h20HYPERLINK\l"_Toc188801011"3.5.3创建多个图象PAGEREF_Toc188801011\h20HYPERLINK\l"_Toc188801012"3.5.4子图象PAGEREF_Toc188801012\h21HYPERLINK\l"_Toc188801013"3.5.5对画线的增强控制PAGEREF_Toc188801013\h22HYPERLINK\l"_Toc188801014"3.5.6文本字符串的高级控制PAGEREF_Toc188801014\h22HYPERLINK\l"_Toc188801015"3.5.7极坐标图象PAGEREF_Toc188801015\h23HYPERLINK\l"_Toc188801016"例3.5PAGEREF_Toc188801016\h24HYPERLINK\l"_Toc188801017"例3.6PAGEREF_Toc188801017\h25HYP