What Are the Different Flowchart Structures?


One of the best tools for designing how a machine may respond to a series of events and interactions that are possible in a procedural system is known as a flowchart diagram. A flowchart is especially useful when designing a software program for a procedural programming language. A flowchart can be used to better ensure that a program is prepared for any situation. Four primary structures can be used to create virtually any flowchart.


  • A sequence is a flowchart structure that represents a series of steps to be performed one after another. It is probably the most basic flowchart concept and is commonly used outside of flowchart design in the form of any sequential step-by-step guide. Some common sequence structures are everyday things like a recipe for making bread, instructions for assembling a toy, or driving directions to a location. Should a sequence structure be all that is necessary in a flowchart diagram being designed, perhaps a numbered list is more appropriate than a flowchart. However, if a conceptual list of steps or instructions needs to account for things like potential detours for road construction while driving, then a flowchart can be much more useful to illustrate alternative routes and choices.


  • The decision structure in a flowchart diagram is used when there is appropriately a decision to be made about how to proceed according to what the current state of program data or progress of a project actually is. A decision structure is also known as a conditional. In programming, a conditional is a common tool used to help a program make a decision about what to do. A conditional is also known as an "if, then" statement in programming languages. For instance, if a user has clicked a certain button on the screen already, then go to step 1. If a user has not clicked the button, then go to step 2. A streetlight on a road is similar to the concept of a decision structure. If the light is green, then go. If it is red, then stop.


  • The loop structure is used in a flowchart to indicate where a program or person should repeat multiple steps until a certain condition is present. For instance, if a program is going to make a stack of 10 circles appear on the screen prior to continuing, then a loop structure would say to see how many circles are on screen and then make more until there are 10. Then it would proceed out of the loop. A more everyday example could be a person saving up to purchase an item. After every bank deposit, they may look at the balance to see if they are ready to make the purchase. It should be noted that a task in a flowchart loop structure can be completed before or after the step where the current condition is requested.


  • The case structure is basically a decision structure with more than two possible situations. A decision structure is good for deciding on buying white or wheat bread, depending on which of the two your family prefers. A case structure is better for when choosing from a wide variety of jelly beans, depending on what kind of jelly bean they like.

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