数值变量转换为字符变量时前面都有空格。

!!和||地作用是一样地

2楼正解，这个是sas base programming 中的一个考点

A rather than B, because:

An automatic data conversion is performed whenever a numeric variable is used where SAS expects a character value. The numeric variable is written with the BEST12. format and the resulting character value is right-aligned when the conversion occurs. In this example, the value of Phonenumber is converted to character and right-aligned before the SUBSTR function is performed. Since there are only 10 digits in the value of Phonenumber, the right-aligned value begins with two blanks. Therefore the SUBSTR function picks up two blanks and a 3, and uses the BEST12. format to assign that value to Code. Then, the parentheses are concatenated before and after the two blanks and a 3.

这就是考试中需要注意的地方，很多小陷阱