What Are Flowcharts?

Flowcharts are diagrammatic representations of a process, algorithm, or system in which geometric symbols represent operations or decision points and arrows indicate the direction of flow between them. They serve as a visual language for documenting logic and procedures, allowing engineers, programmers, and analysts to communicate process structure without reference to a specific implementation language or platform. The concept traces to Frank Gilbreth, who introduced the "flow process chart" to members of the American Society of Mechanical Engineers in 1921 as a method for industrial process documentation. Herman Goldstine and John von Neumann later applied the technique to computer program design in the late 1940s, establishing flowcharts as a core tool of software development.

Flowcharts draw from both industrial engineering and computer science. Their notation was formalized in the 1960s and 1970s, and the ISO 5807:1985 standard later codified the symbol set used for information processing diagrams, including the rectangle for process steps, the diamond for decision branches, the oval for start and end terminals, and the parallelogram for input and output.

Symbols and Notation

Each symbol in a flowchart carries a defined meaning tied to a class of operation. The rectangle represents a computation or action step. The diamond represents a conditional test, with two or more branches emerging from its vertices to capture yes/no or multiple-outcome decisions. Connector circles link distant sections of a large diagram without requiring a drawn line across the page. Flowchart symbols are standardized in the IEEE Computer Society's Software Engineering Body of Knowledge (SWEBOK) as well as in ISO 5807, giving the notation cross-disciplinary consistency.

Flowcharts in Programming and Algorithm Design

In programming, flowcharts function as a planning and documentation tool that precedes or accompanies implementation. A programmer drafts a flowchart to map the logical structure of an algorithm, identifying loops, branches, and data transformations before writing code. For teaching purposes, flowcharts make algorithmic thinking visible: a student tracing the arrows through a sorting routine develops an intuition for iteration and conditional logic that abstract pseudocode alone does not always provide. Research into visual programming environments has demonstrated that flowchart-based interfaces reduce entry barriers for novice developers while preserving expressive power for moderately complex programs.

For more complex systems, flowcharts remain useful as high-level overviews even when detailed implementation is expressed in structured text or formal specification languages. A data-flow diagram is a direct extension of the flowchart concept, replacing sequential control arrows with representations of data movement between processes.

Control Flow and Structured Programming

The relationship between flowcharts and structured programming is historically significant. The structured programming movement of the late 1960s, associated with Edsger Dijkstra and the work published as the NATO Software Engineering conferences, argued that programs constructed from three control structures (sequence, selection, and iteration) were more readable and correct than programs using unrestricted branching. Every structured program corresponds to a flowchart using only these three patterns, which gives flowcharts a direct connection to program correctness reasoning. Flowcharts also underpin work in formal verification, where control flow graphs, derived directly from flowchart representations, are traversed by tools checking reachability, loop bounds, and data-flow properties.

Applications

Flowcharts have applications in a range of fields, including:

• Software development, for planning algorithms and documenting program logic
• Systems analysis and business process modeling
• Quality assurance and process improvement frameworks such as Six Sigma
• Embedded and real-time systems design for documenting control sequences
• Educational computing, for teaching algorithmic reasoning and program structure