## DO loop basics

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Occasional Contributor
Posts: 12

# DO loop basics

```data WORK.LOOP;
X = 0;
do Index = 1 to 5  by  2;
X = Index;
end;
run;```

Upon completion of execution, what are the values of the variables X and Index in the SAS data set named WORK.LOOP?

1. X = 3, Index = 5
2. X = 5, Index = 5
3. X = 5, Index = 6
4. X = 5, Index = 7

I knew the answer was X=5 and index=7;

Question is : When the index =5, isn't  the program stop executing DO loop and gives the answer of index=5 and x=5.However, the answer was X=5 and index=.How??????

Accepted Solutions
Solution
‎05-08-2017 08:32 AM
Super User
Posts: 9,611

## Re: DO loop basics

A do loop works like that:

1 - set the iteration variable to the start value

2 - compare to the end value

3 - if less or equal to the end value (greater or equal if the by value is negative), enter the body of the do, otherwise goto 6

4 - at the end of the body, increment by the by value

5 - goto 2

6 - end

So you see that the iteration variable needs to exceed the end value to terminate the iterative do loop.

---------------------------------------------------------------------------------------------
Maxims of Maximally Efficient SAS Programmers
How to convert datasets to data steps
How to post code

All Replies
Solution
‎05-08-2017 08:32 AM
Super User
Posts: 9,611

## Re: DO loop basics

A do loop works like that:

1 - set the iteration variable to the start value

2 - compare to the end value

3 - if less or equal to the end value (greater or equal if the by value is negative), enter the body of the do, otherwise goto 6

4 - at the end of the body, increment by the by value

5 - goto 2

6 - end

So you see that the iteration variable needs to exceed the end value to terminate the iterative do loop.

---------------------------------------------------------------------------------------------
Maxims of Maximally Efficient SAS Programmers
How to convert datasets to data steps
How to post code
Occasional Contributor
Posts: 12

## Re: DO loop basics

Thanks mr.KurtBremser.I am still in the learning curve.

Senior User
Posts: 1

## Re: DO loop basics

Thanks for explaining.

Super User
Posts: 13,084