$ whois ladder-logic

Ladder Logic

first released in 1969 · by Dick Morley

$ guessprog --inspect ladder-logic

year: 1969
paradigm: visual
family: other
memory: none
binding: static
safety: strong

LADDER-LOGIC(7)

AUTHORS: Dick Morley
HISTORY: Ladder diagrams began as a way to document the relay racks that controlled factory machinery, drawn as two power rails joined by horizontal rungs. In 1968 General Motors' Hydra-Matic division asked for a programmable replacement for its hard-wired relay panels, and Dick Morley's team at Bedford Associates answered in 1969 with the Modicon 084, one of the first programmable logic controllers. Programming PLCs with the same ladder notation let electricians reuse what they already knew. The notation was later standardised as Ladder Diagram (LD) in IEC 61131-3.
USAGE: Still one of the most widely used languages in industrial automation, found on PLCs running assembly lines, packaging machines, pumps and conveyors around the world. It is mostly written and maintained by controls engineers and plant technicians.
SEE ALSO: Ladder Logic on Wikipedia ↗

$ cat motor_start_stop.ld.txt

Motor start/stop with seal-in
] [ = normally open contact, ]/[ = normally closed, ( ) = coil

     START       STOP                  MOTOR
 |----] [----+----]/[-------------------( )----|
 |           |                                 |
 |   MOTOR   |                                 |
 |----] [----+                                 |
 |                                             |
 |    MOTOR                             LAMP   |
 |----] [-------------------------------( )----|