What is the difference between do until and do while

Here, SAS evaluates the condition at the bottom of the loop. A huge difference in processing between the two loops. This rule may not come as a surprise, but it is still nice to remember. The Do Until loop keeps iterating while the condition is false and until the condition is true. The Do While loop simply executes as long as the condition is true.

Examine the code above and verify that you understand this. For the DO-group to be repeated, the expression must have a false value. If the expression has a true value, control passes to the next executable statement following the END statement that terminates the DO-group. Send feedback about this topic. Also there's a significant difference between post-test loops code block will execute at least once and pre-test loops code block may be skipped over entirely. Repeat the loop until condition is False.

Until Required unless While is used. Repeat the loop until condition is True. Polywhirl Mr. Polywhirl The question was about the difference between Do While and Do Until , not about the difference between pre-test and post-test loops.

The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming The condition is verified and, if it is true, the loop is iterated again, and if the condition is false, then the control resumes to the next line immediately after the loop. Both while and do-while loop are the iteration statement, if we want that first, the condition should be verified, and then the statements inside the loop must execute, then the while loop is used.

If you want to test the termination condition at the end of the loop, then the do-while loop is used. I loved this page very nicely presented and easy answers with key points covered in it……. Your email address will not be published. Key Differences Between while and do-while Loop The while loop checks the condition at the starting of the loop and if the condition is satisfied statement inside the loop, is executed. As against, in the do-while loop, the condition is checked after the execution of all statements in the body of the loop.

If the condition in a while loop is false, not a single statement inside the loop is executed. The while loop is also known as the entry-controlled and pre-checking loop because in this loop, the body of the loop is executed prior to checking the condition. Conversely, the alternate name for the do-while loop is the exit-controlled and post-checking loop, the reason behind this is that the checking of the loop condition is followed by the execution of the body of the loop.