【LAPTHW】习题 4：变量和命名-pantierui-ChinaUnix博客

你已经学会了Dsply和算术运算。下一步你要学的是“变量”。在编程中，变量只不过是用来指代某个东西的名字。程序员通过使用变量名可以让他们的程序读起来更像英语。而且因为程序员的记性都不怎么地，变量名可以让他们更容易记住程序的内容。如果他们没有在写程序时使用好的变量名，在下一次读到原来写的代码时他们会大为头疼的。

如果你被这章习题难住了的话，记得我们之前教过的：找到不同点、注意细节。

在每一行的上面写一行注解，给自己解释一下这一行的作用。
倒着读你的RPGLE文件。
朗读你的RPGLE文件，将每个字符也朗读出来。

EX4

0001.00 D Cars            S             10S 0
0002.00 D Space_in_a_car S             10S 1
0003.00 D Drivers         S             10S 0
0004.00 D passengers      S             10S 0
0005.00 D Cars_not_driven...
0006.00 D                 S             10S 0
0007.00 D Carpool_capacity...
0008.00 D                 S             10S 1
0009.00 D Average_passengers_per_car...
0010.00 D                 S             10S 0
0011.00 D Cars_driven     S             10S 0
0012.00 D String          S             51A
0013.00 D Wait            S              1A
0014.00 C                   Eval      Cars = 100
0015.00 C                   Eval      Space_in_a_car = 4.0
0016.00 C                   Eval      Drivers = 30
0017.00 C                   Eval      Passengers = 90
0018.00 C                   Eval      Cars_not_driven = Cars - Drivers
0019.00 C                   Eval      Cars_driven = Drivers
0020.00 C                   Eval      Carpool_capacity = Cars_driven *
0021.00 C                                                Space_in_a_car
0022.00 C                   Eval      Average_passengers_per_car = Passengers /
0023.00 C                                                          Cars_driven
0024.00 C*
0025.00 C                   Eval      String = 'There are ' + %char(Cars) +
0026.00 C                                      ' cars available.'
0027.00 C     String        Dsply
0028.00 C                   Eval      String = 'There are only ' +
0029.00 C                                      %char(Drivers) +
0030.00 C                                      ' drivers available.'
0031.00 C     String        Dsply
0032.00 C                   Eval      String = 'There will be ' +
0033.00 C                                      %char(Cars_not_driven) +
0034.00 C                                      ' empty cars today.'
0035.00 C     String        Dsply
0036.00 C                   Eval      String = 'We can transport ' +
0037.00 C                                      %char(Carpool_capacity) +
0038.00 C                                      ' people today.'
0039.00 C     String        Dsply
0040.00 C                   Eval      String = 'We have ' +
0041.00 C                                      %char(Passengers) +
0042.00 C                                      ' to carpool today.'
0043.00 C     String        Dsply
0044.00 C                   Eval      String = 'We need to put about ' +
0045.00 C                                      %char(Average_passengers_per_car) +
0046.00 C                                      ' in each car.'
0047.00 C     String        Dsply                   Wait
0048.00 C*
0049.00 C                   Eval      *inlr = *on
0050.00 C                   Return

EX4F

0001.00 D Cars S 10S 0

0002.00 D Space_in_a_car S 10S 1

0003.00 D Drivers S 10S 0

0004.00 D passengers S 10S 0

0005.00 D Cars_not_driven...

0006.00 D S 10S 0

0007.00 D Carpool_capacity...

0008.00 D S 10S 1

0009.00 D Average_passengers_per_car...

0010.00 D S 10S 0

0011.00 D Cars_driven S 10S 0

0012.00 D String S 51A

0013.00 D Wait S 1A

0014.00 /free

0015.00 Cars = 100;

0016.00 Space_in_a_car = 4.0;

0017.00 Drivers = 30;

0018.00 Passengers = 90;

0019.00 Cars_not_driven = Cars - Drivers;

0020.00 Cars_driven = Drivers;

0021.00 Carpool_capacity = Cars_driven * Space_in_a_car;

0022.00 Average_passengers_per_car = Passengers / Cars_driven;

0023.00

0024.00 String = 'There are ' + %char(Cars) + ' cars available.';

0025.00 Dsply String;

0026.00 String = 'There are only ' + %char(Drivers) + ' drivers available.';

0027.00 Dsply String;

0028.00 String = 'There will be ' + %char(Cars_not_driven) +

0029.00 ' empty cars today.';

0030.00 Dsply String;

0031.00 String = 'We can transport ' + %char(Carpool_capacity) +

0032.00 ' people today.';

0033.00 Dsply String;

0034.00 String = 'We have ' + %char(Passengers) + ' to carpool today.';

0035.00 Dsply String;

0036.00 String = 'We need to put about ' +

0037.00 %char(Average_passengers_per_car) +

0038.00 ' in each car.';

0039.00 Dsply String '' Wait;

0040.00

0041.00 *inlr = *on;

0042.00 return;

0043.00

0044.00 /end-free

当我刚开始写这个程序时我犯了个错误，RPGLE 告诉我这样的错误信息：

20 D Carpool_capacity...

21 D S 10S 0

……

33 C Eval Car_pool_capacity = Cars_driven *

34 C Space_in_a_car

*RNF7030 30 1 The name or indicator is not defined.

*RNF7030 30 33 003300 The name or indicator CAR_POO... is not defined.

用你自己的话解释一下这个错误信息，解释时记得使用行号，而且要说明原因。

RPGLE中变量名是不区分大小写的。

更多的加分习题:

1. 如何查看编译错误。试一试命令WRKSPLF，然后按SHIFT+F6，看看能找到什么信息

2. 在每一个变量赋值的上一行加上一行注解

3. 记住 = 的名字是等于(equal)，它的作用是为东西取名

4. 记住 _ 是下划线字符(underscore)

5. 函数%char（）的作用是什么，为什么使用它