Sequence control using contact relays was dominant in the 1960s. However, this type of sequence control was extremely time‑consuming. Making a change in the control circuits whenever the device, equipment, or production system was replaced or updated was very complicated.

Meanwhile, the requirements for a new sequence control system to replace the one using contact relays were presented by an automobile manufacturer in the United States. As a result, the first programmable controller was developed as a controller that satisfies those requirements.