Flowchart symbols
The standard flowchart shapes, from the oval terminal and the decision diamond to the document and connector, and what each one means.
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About flowchart symbols
A flowchart is a diagram of the steps of a process, drawn as standard shapes joined by lines in the order the steps happen. The American standard for flowchart symbols, ANSI X3.5-1970, defines it as a graphical representation of the definition, analysis or solution of a problem, in which symbols stand for operations, data, flow and equipment; the international standard, ISO 5807:1985, uses nearly the same words. Each shape has its own meaning: a rounded Terminal (start and end) starts and ends the chart, a rectangle is a Process step, a diamond is a Decision where the path branches, and a parallelogram is Input/output (data). Lines between them are flowlines, read from left to right and top to bottom. Each symbol has its own page.
Where the shapes come from
The shapes were standardised as computers spread through business. The foreword to ANSI X3.5-1970 records that flowcharts became widespread with electronic computers in business and industry, and that charts were sometimes misread because the same symbol meant different things to different groups. Companies, user groups, equipment makers and form suppliers had each drawn up their own sets. A Jet Propulsion Laboratory report dates the first proposal for a standard to 1963. An American standard followed in 1966, revised in 1968 and again in 1970, when its definitions were brought into line with the International Organization for Standardization’s Recommendation R 1028 of 1969. The US federal government adopted X3.5-1970 as a Federal Information Processing Standard in 1973. IBM, which published its own flowcharting manual, sold a plastic template with cutouts for every symbol, to encourage everyone to draw them the same way. ISO 5807, published in 1985, brought ISO 1028 and ISO 2636 together and replaced them.
Program and system flowcharts
IBM’s manual distinguishes two kinds of chart. A system flowchart follows data through all parts of a system, so it puts the emphasis on the media, such as cards, tape and documents, and the work stations they pass through. A program flowchart is a diagram of the operations and decisions in a program and the order in which the computer performs them. ISO 5807 also covers data flowcharts and other charts with the same symbols.
Basic and specialised symbols
ANSI X3.5-1970 gives each function a basic symbol that, in its words, “can always be used”: the parallelogram for input and output, the rectangle for processing. Specialised symbols can replace them to say more, such as a Document for printed output or Manual input for a keyboard. ANSI X3.5-1970 allows the curves and angles of a shape to vary slightly, as long as the shape stays recognisable. Some shapes in everyday use come from IBM rather than the standards: the five-sided Off-page connector is in IBM’s manual, while the 1970 standard uses the round Connector for page breaks too.
Sources
- Flowchart Symbols and Their Usage in Information Processing, ANSI X3.5-1970, adopted for federal use as FIPS PUB 24, American National Standards Institute; National Bureau of Standards (NIST), Foreword; sections 2, 3.1 and 4.1
- Information processing: Documentation symbols and conventions for data, program and system flowcharts, program network charts and system resources charts, ISO 5807:1985, first edition (preview pages), International Organization for Standardization (iTeh Standards preview), Sections 0 and 3.3
- Flowcharting Techniques, IBM Data Processing Techniques, Form C20-8152, International Business Machines Corporation (bitsavers.org), Introduction; Flowcharting template; System flowcharts; Program flowcharts
- Flowcharting with D-Charts, JPL Publication 84-99, Donald D. Meyer, Jet Propulsion Laboratory, NASA (Internet Archive), Section 1
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research