Flowcharts

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LampFlowchart — 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.

Examples include instructions for a bicycle's assembly, an attorney outlining a case's timeline, diagram of an automobile plant's work flow, the decisions to be taken on a tax form, et cetera.

Generally the start point, end points, inputs, outputs, possible paths and the decisions that lead to these possible paths are included.

Flow-charts can be created by hand or manually in most office software, but lately specialized diagram drawing software has emerged that can also be used for the purpose. See below for examples.

Nassi-Schneiderman diagrams are (almost) isomorphic with flowcharts. These are one of many Structured Flow Charts. Everything that can be represented using them, you can also represent using a normal unstructured flowchart. For flowcharts of programs, just about everything you can represent with a flowchart you can also represent with a similar Nassi-Schneiderman diagram. The exceptions are things like goto, and the C programming language loop break and continue statements. However, in 1966, Corrado Bohm & Giuseppe Jacopini proved that a more complex structured flow chart can define the same process as any given flow chart (Commun ACM V9n5(May 1966) pp366-71).

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 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 (versions 97 through 2003), OpenOffice.org Draw, EDraw Flowchart Software, Inkscape, ConceptDraw and SmartDraw have specialized tools for making consistent charts.

When in Microsoft Word, enable the Drawing toolbar and click Autoshapes then Flowcharts and finally on the appropriate shape you would like. Right-click on a shape and then click Add Text to do so. The Arrow or Line tool is used to manually draw links. The connectors are not available in Word 97 or 2000 - so lines will not remain connected to objects if they are moved. (They are available in Excel 2000 and PowerPoint 2000, just not Word.)

You can also create Flowcharts directly in Excel (useful for printing in large papers) and in PowerPoint (useful for presentations). The functions in these programs are much the same as the Word functions. (In Microsoft Office 2000, Excel and PowerPoint have connectors where Word does not.)

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.

Creating flowcharts can also be done with Microsoft Visio, part of the Microsoft Office Suite of applications.

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:

Lava lamp flowchart — 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[]

FlowchartExample — 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.)

External links[]

Flowcharting Techniques, an IBM manual from 1969 (5MB PDF format)
Introduction to Programming in C++ flowchart and pseudocode (PDF)
Examples (Spanish)
Opensource Javascript Flowchart Tool

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