A diagnostic program (also known as a test mode) is an automatic computer program sequence that determines the operational status within the software, hardware, or any combination thereof in a component, a system, or a network of systems. Diagnostic programs ideally provide the user with guidance regarding any issues or problems found during its operation. Diagnostics programs may be simple or complex, operating unknowingly within everyday devices or awaiting their invocation to make more complex performance assessments. Everyday examples are a microwave oven that displays code F6 to warn of a shorted temperature probe or a garage door opener that flashes its control board's LED four times warning of critically misaligned safety sensors and impending shutdown. Diagnostic programs are also inserted into consumer electronic products and electronic games. Sometimes if the owner of an electronic device asks the manufacturer how to access the hidden diagnostic program, they may reply to the consumer saying that the information is considered to be "proprietary" and cannot be shared.

History

Early diagnostics programs were procedural instructions performed by humans, not by computer programs. See Built-in test equipment that enabled system operators to perform testing and diagnostics. As computers became smaller, more mobile, computer programs were used to perform diagnostics tasks. In the late 1960s, Volkswagen introduced the first on-board computer system with diagnostics provisions.

Methods of operation

The diagnostics program for a device or system may be independently located or integrated within. These Methods of Operation are arranged, more-or-less, in order of increasing complexity and their increasing value of diagnostics information.

Architectures

Example diagnostics program applications