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Flowchart

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A simple flowchart for what to do if a lamp doesn't work

A flowchart (also spelled flow-chart and flow chart) is a schematic representation of an algorithm or a process.

The flowchart is one of the seven basic tools of quality control, which include the histogram, Pareto chart, check sheet, control chart, cause-and-effect diagram, flowchart, and scatter diagram. See Quality Management Glossary. They are commonly used in business/economic presentations to help the audience visualize the content better, or to find flaws in the process.

Symbols

A typical flowchart from older Computer Science textbooks may have the following kinds of symbols:

  • Start and end symbols, represented as lozenges, ovals or rounded rectangles, usually containing the word "Start" or "End", or another phrase signaling the start or end of a process, such as "submit enquiry" or "receive product".
  • Arrows, showing what's called "flow of control" in computer science. An arrow coming from one symbol and ending at another symbol represents that control passes to the symbol the arrow points to.
  • Processing steps, represented as rectangles. Examples: "Add 1 to X"; "replace identified part"; "save changes" or similar.
  • Input/Output, represented as a parallelogram. Examples: Get X from the user; display X.
  • Conditional (or decision), represented as a diamond (rhombus). These typically contain a Yes/No question or True/False test. This symbol is unique in that it has two arrows coming out of it, usually from the bottom point and right point, one corresponding to Yes or True, and one corresponding to No or False. The arrows should always be labeled. More than two arrows can be used, but this is normally a clear indicator that a complex decision is being taken, in which case it may need to be broken-down further, or replaced with the "pre-defined process" symbol.
  • A number of other symbols that have less universal currency, such as:
    • A Document represented as a rectangle with a wavy base;
    • A Manual input represented by rectangle, with the top irregularly sloping up from left to right. An example would be to signify data-entry from a form;
    • A Manual operation represented by a trapezoid with the longest parallel side utmost, to represent an operation or adjustment to process that can only be made manually.
    • A Data File represented by a cylinder
  • Note: All process symbols within a flowchart should be numbered. Normally a number is inserted inside the top of the shape to indicate which step the process is within the flowchart.

Flowcharts may contain other symbols, such as connectors, usually represented as circles, to represent converging paths in the flow chart. Circles will have more than one arrow coming into them but only one going out. Some flow charts may just have an arrow point to another arrow instead. These are useful to represent an iterative process (what in Computer Science is called a loop). A loop may, for example, consist of a connector where control first enters, processing steps, a conditional with one arrow exiting the loop, and one going back to the connector. Off-page connectors are often used to signify a connection to a (part of a) process held on another sheet or screen. It is important to remember to keep these connections logical in order. All processes should flow from top to bottom and left to right.

A flowchart is described as "cross-functional" when the page is divided into different "lanes" describing the control of different organizational units. A symbol appearing in a particular "lane" is within the control of that organizational unit. This technique allows the analyst to locate the responsibility for performing an action or making a decision correctly, allowing the relationship between different organizational units with responsibility over a single process.

Software

Manual

There are various packages for manually and automatic creating flowcharts, according to different standards. The most common is UML, for which there are abundant packages for various platforms. See UML article for a list. The creation of simple flowcharts on a computer is fairly easy with any vector-based drawing program, but Microsoft Word, OpenOffice.org Draw, EDraw Flowchart Software, Inkscape, Dia, ConceptDraw, and SmartDraw are all widely used for this purpose.

When in OpenOffice.org, enable the Drawing toolbar which has a flow-out menu for Flowcharts since version 2.0, which can do roughly the same as Word.

When in OpenOffice.org Draw, enable the Flowchart palette and click a shape to add it in. Double-clicking a shape will add text to it within appropriate boundaries. Connections can be automatically made between shapes using Connectors and Glue Points - click on the Connector arrow to see a selection of them before dragging from a Glue Point on a shape to another. Draw will maintain the link and automatically redraw the connector if you resize or move any shape.

When in Microsoft Visio, select Basic Flowchart from the Flowchart category for the most common symbols.

Auto

Many software packages exist that can create flowcharts automatically, either directly from source code, or from a flowchart description language:

Examples, Graph::Easy, a Perl package, takes a textual description of the graph, and turns it into various output formats like HTML, ASCII or SVG. The example graph at the top of the page and listed below would be described like the text shown below. The automatically generated SVG output is shown on the right:

A simple flowchart, created automatically.
graph         { flow: south; }
node.start    { shape: rounded; fill: #ffbfc9; }
node.question { shape: diamond; fill: #ffff8a; }
node.action   { shape: rounded; fill: #8bef91; }

[ Lamp doesn't work ] { class: start }
  --> [ Lamp\n plugged in? ] { class: question; }
   -- No --> [ Plug in lamp ] { class: action; }

[ Lamp\n plugged in? ]
  --> [ Bulb\n burned out? ] { class: question; }
   -- Yes --> [ Replace bulb ] { class: action; }

[ Bulb\n burned out? ]
  -- No --> [ Buy new lamp ] { class: action; }

There exist also various MediaWiki Extensions to incorporate flowchart descriptions directly into wiki articles. This is then automatically turned into the desired output format.

Examples

A simple flowchart for computing factorial N (N!)

A flowchart for computing factorial N (N!) Where N! = 1 * 2 * 3 * …… N. This flowchart would be difficult to program directly into a computer programming language since most programming languages branch on "yes" or "true" and continue on "no" or "false". Further, the flowchart represents "a loop and a half" — a situation discussed in introductory programming textbooks that requires either a duplication of a component (to be both inside and outside the loop) or the component to be put inside a branch in the loop.

Since computer programming languages do not contain all of the constructs that can be created by the drawing of flowcharts, they do not often help new programmers learn the concepts of logical flow and program structure. To try writing flowcharts for computer programs, an on-line applet for iconic programming is available that limits the flowchart components and connections to those that can be directly converted into any programming language. (Note: click on the yellow square to begin.)

See also

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