Glossary · Automation software engineering and architecture
Thread
Also known as: Thread of execution, Lightweight process
German: Thread
In computing, a thread is the smallest unit of execution that an operating system schedules, running within a process and sharing that process's memory and resources with its other threads.
- Software engineering
In one sentence
A thread is the smallest unit of execution an operating system schedules, running inside a process and sharing its memory.
Example
The OPC UA server runs one thread per client session and a separate thread that samples the PLC variables.
How it applies
- Engineering: Threads allow concurrent work within one program. Because they share memory, access to shared data must be synchronized.
- Real-time systems: In an RTOS, threads are often called tasks and have fixed priorities. Thread count and priorities are part of the timing design.
- Documentation: Architecture documentation should list threads, priorities and responsibilities. In user documentation, threads rarely appear, except where users configure them, such as worker threads of a server.
Thread vs. digital thread
A thread is a unit of program execution. The Digital thread is an unrelated systems engineering concept: the connected flow of data across a product's lifecycle. Avoid the bare word thread where both meanings could occur.