the condition. There are two main types of testing loops, test first and test last blocks. The only difference between the two is the order in which the steps involved are completed. In the test first situation, when the program encounters the block it tests to see if the condition is fulfilled, then, if it is not completes the process blocks and then loops back. The test is performed again and, if the condition is still unfulfilled, it processes again. If at any stage the condition is fulfilled the program skips the process blocks and continues onto the next block. The test last block is simply reversed, the process blocks are completed before the test is performed. The test last loop allows for the process blocks to be performed at least once before the first test. Parallel execution can be drawn like this: See also Drakon-chart Flowchart Pseudocode Publications Nassi, I.; Shneiderman, B.: Flowchart techniques for structured programming, SIGPLAN Notices XII, August 1973. References External links A short history of structured flowcharts (Nassi–Shneiderman Diagrams), by Ben Shneiderman, draft, 27 May 2003. Nicholas Hebb: "How to Create a Nassi-Shneiderman Diagram in Excel" (no date). Jülich Supercomputing Centre (JSC): "Generation of Nassi-Shneiderman Diagrams under Unix with nassi", 30 October 2012. Yoder, Cornelia M; Schrag, Marilyn L.: "Nassi-Shneiderman Charts: An Alternative to Flowcharts for Design". Proceedings, ACM SIGSOFT/BIGMETRICS Software and Assurance Workshop, November 1978. Computer programming Diagrams