The following SAS program is submitted:
data work.clients;
calls = 6;
do while (calls le 6);
calls + 1;
end;
run;
Which one of the following is the value of the variable CALLS in the output data set?
A. 4
B. 5
C. 6
D. 7
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D
ReplyDeleteD
ReplyDeleteHi....Why is it 7 ?? calls i not less than 6 ??
ReplyDeleteDO WHILE (evaluates at the top of the loop) Now, calls=6 is equal to 6 therefore calls le 6 is TRUE. DO LOOP is executed. So, calls = calls +1 = 7
DeleteNow, calls=7 is greater than 6 therefore calls le 6 is FALSE. DO LOOP is not executed.
Hence, the value of calls remains 7
le means "less than or equal to"
Deleteplz write the comments
ReplyDeletethe answer is D, because 'le' means "less than or equal".
ReplyDeleteCalls=6
ReplyDeleteSo the program will execute once, and add 1 to calss to get to 7, because the condition says: While calls LE 6.
Calls = 7
ReplyDeleteanswer = D
A while condition isn't checked until the end of the loop, so the first time through, +1 is added to calls, resulting in 6- then the condition is checked and it stops.
ReplyDeleteAnswer is D
you are confused.
Deletedo until is not evaluated until the bottom of the loop
and
do while is evaluated at the top of the loop
Sakar Sham;
ReplyDeleteSo in "while" condition it checks up to 6 then it stops. We would not forget it. Thank you.
How about if replaced by "until"? It must be in the question somewhere?
Answer is D. 7
ReplyDeletehere, note that the operator is LE (less than or equal to). So the condition is true the first time.
Calls = 6 and it becomes Calls + 1 => 6+1 = 7.
The loop stops executing as the value of calls becomes greater than 6. Thus, output is 7.
Please note the difference between do while and do until:
ReplyDeleteDO WHILE
The while test is evaluated at the top of the loop.
DO UNTIL
The until test is evaluated at the bottom of the loop.
Reference: http://www2.sas.com/proceedings/forum2007/067-2007.pdf
The change should be change in the following manner to obtain the same results using a do until loop:
data clients;
calls = 6;
do until (calls GE 6);
calls + 1;
end;
run;
Not that the difference here is DO WHILE uses Calls LE 6 and DO UNTIL uses Calls GE 6.
The example provided in the reference helps understand this better.
D
ReplyDeleteD, 7
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do while loop is looking for where to stop which is when it counters false and that is when calls +1 < 6 (simple math) and that would be when calls =7 and that should be the desired output(checking when to stop).
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