问两道SAS Base题目

问两道SAS Base题目
40.The following SAS program is submitted:
data work.pieces;
do while (n lt 6);
n + 1;
end;
run;
What is the value of the variable N in the output data set?
A.5
B.6
C.7
D..(missing numeric)
Answer:B
为什么答案选B?一开始n没有被定义啊,在do while里n应该是missing啊.你在n+1的时候才被赋值为0的吧……
48.Given the raw data file CALENDAR:
----|----10---|----20---|----30
01012000
The following SAS program is submitted:
data test;
infile 'calendar';
input @1 date mmddyy10.;
if date = '01012000'd then event = 'January 1st';
run;
What is the value of the EVENT variable?
A.' ' (missing character value)
B..(missing numeric value)
C.January 1st
D.The program fails to execute due to errors.
虽然mmddyy10.的读取长度过长了,但是我在SAS程序上涌datalines的方式试了一下还是能够读取的啊,为什么答案说会有错误?