What is a flow chart?
A flowchart is a type of diagram that represents an algorithm, workflow or process, showing the steps as boxes of various kinds, and their order by connecting them with arrows. This diagrammatic representation illustrates a solution model to a givenproblem. Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.
Flowcharts are used in designing and documenting complex processes or programs. Like other types of diagrams, they help visualize what is going on and thereby help the people to understand a process, and perhaps also find flaws, bottlenecks, and other less-obvious features within it. There are many different types of flowcharts, and each type has its own repertoire of boxes and notational conventions. The two most common types of boxes in a flowchart are:
Overview
Flowcharts are used in designing and documenting complex processes or programs. Like other types of diagrams, they help visualize what is going on and thereby help the people to understand a process, and perhaps also find flaws, bottlenecks, and other less-obvious features within it. There are many different types of flowcharts, and each type has its own repertoire of boxes and notational conventions. The two most common types of boxes in a flowchart are:
- a processing step, usually called activity, and denoted as a rectangular box
- a decision, usually denoted as a diamond.
A flowchart is described as "cross-functional" when the page is divided into different swimlanes 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 author to locate the responsibility for performing an action or making a decision correctly, showing the responsibility of each organizational unit for different parts of a single process.
Flowchart building blocks
Symbols
FlowChart Symbols List A typical flowchart from older basic computer science textbooks may have the following kinds of symbols:
- Represented as circles, ovals or rounded (fillet) rectangles, usually containing the word "Start" or "End", or another phrase signaling the start or end of a process, such as "submit inquiry" or "receive product".
Start and end symbols
- Showing "flow of control". An arrow coming from one symbol and ending at another symbol represents that control passes to the symbol the arrow points to. The line for the arrow can be solid or dashed. The meaning of the arrow with dashed line may differ from one flowchart to another and can be defined in the legend.
Arrows
- Represented as rectangles. Examples: "Add 1 to X"; "replace identified part"; "save changes" or similar.
Generic processing steps
- Represented as rectangles with double-struck vertical edges; these are used to show complex processing steps which may be detailed in a separate flowchart. Example: process-files. One subroutine may have multiple distinct entry points or exit flows (see coroutine); if so, these are shown as labeled 'wells' in the rectangle, and control arrows connect to these 'wells'.
Subroutines
- Represented as a parallelogram. Examples: Get X from the user; display X.
Input/Output
- Represented as a hexagon. Shows operations which have no effect other than preparing a value for a subsequent conditional or decision step (see below).
Prepare conditional
- Represented as a diamond (rhombus) showing where a decision is necessary, commonly a Yes/No question or True/False test. The conditional symbol is peculiar 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.
Conditional or decision
- Generally represented with a black blob, showing where multiple control flows converge in a single exit flow. A junction symbol will have more than one arrow coming into it, but only one going out.
- In simple cases, one may simply have an arrow point to another arrow instead. These are useful to represent an iterativeprocess (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.
- For additional clarity, wherever two lines accidentally cross in the drawing, one of them may be drawn with a small semicircle over the other, showing that no junction is intended.
Junction symbol
- Represented by an identifying label inside a circle. Labeled connectors are used in complex or multi-sheet diagrams to substitute for arrows. For each label, the "outflow" connector must always be unique, but there may be any number of "inflow" connectors. In this case, a junction in control flow is implied.
Labeled connectors
- Represented by a double transverse line with any number of entry and exit arrows. These symbols are used whenever two or more control flows must operate simultaneously. The exit flows are activated concurrently when all of the entry flows have reached the concurrency symbol. A concurrency symbol with a single entry flow is a fork; one with a single exit flow is a join.
Concurrency symbol
All processes should flow from top to bottom and left to right.
Data-flow extensions
A number of symbols have been standardized for data flow diagrams to represent data flow, rather than control flow. These symbols may also be used in control flowcharts (e.g. to substitute for the parallelogram symbol).
- A Document represented as a rectangle with a wavy base;
- A Manual input represented by quadrilateral, 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 at the top, to represent an operation or adjustment to process that can only be made manually.
- A Data File represented by a cylinder.
Types of flowchart
Sterneckert (2003) suggested that flowcharts can be modeled from the perspective of different user groups (such as managers, system analysts and clerks) and that there are four general types:
- Document flowcharts, showing controls over a document-flow through a system
- Data flowcharts, showing controls over a data-flow in a system
- System flowcharts showing controls at a physical or resource level
- Program flowchart, showing the controls in a program within a system
Notice that every type of flowchart focuses on some kind of control, rather than on the particular flow itself.[11]
However there are several of these classifications. For example Andrew Veronis (1978) named three basic types of flowcharts: the system flowchart, the general flowchart, and the detailed flowchart.[12] That same year Marilyn Bohl (1978) stated "in practice, two kinds of flowcharts are used in solution planning: system flowcharts and program flowcharts...".[13]More recently Mark A. Fryman (2001) stated that there are more differences: "Decision flowcharts, logic flowcharts, systems flowcharts, product flowcharts, and process flowcharts are just a few of the different types of flowcharts that are used in business and government".[14]
In addition, many diagram techniques exist that are similar to flowcharts but carry a different name, such as UML activity diagrams.
Software
Diagramming
Any drawing program can be used to create flowchart diagrams, but these will have no underlying data model to share data with databases or other programs such as project management systems or spreadsheet. Some tools offer special support for flowchart drawing. Many software packages exist that can create flowcharts automatically, either directly from a programming language source code, or from a flowchart description language. On-line web-based versions of such programs are available.
Programming
There are several applications that use flowcharts to represent and execute programs. Generally these are used as teaching tools for beginner students.
These include:
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