N-S diagrams
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N-S or Nassi-Schneiderman diagrams are used in the planning process of writing computer programs. The process developed by I. Nassi and B. Schneiderman uses diagrams to represent simply programming steps. N-S Diagrams are a tool used by many programmers to help simplify the programming process. The use of these diagrams along with other similiar planning tools can help break large complex problems down into small easily manageable steps.
Process Blocks The process block represents the simplest of steps and requires no analyses. When a process block is encountered the action inside the block is performed and we move onto the next block.
Branching Blocks There are two types of branching blocks. First is the simple True/False or Yes/No branching block which offers the program two paths to take depending on whether or not a condition has been fulfilled. These blocks can be used as a looping procedure stopping the program from continuing until a condition has been fulfilled.
The second type of branching block is a multiple branching block. This block is used as a select case is needed in a program. The block usually contains a question or select case. The block provides the program with an array of choices and is often used in conjuction with sub process blocks to save space.
Testing Loops
This block allows the program to loop one or a set of process until a particular condition is fulfilled. The process blocks covered by each loop are subset with a side-bar extending out from 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, the 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.
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