A program written in LD consists of a succession of networks run sequentially by the automaton.
A network, drawn between two potential bars, is a set of graphic elements representing :
the inputs/outputs of the automaton (push-buttons, detectors, relay, indicators...) ;
automatism functions ( timers, counters...) ;
arithmetic and logic operations and transfer operations ;
the internal variables of the automaton ;
a network has only one output except for timers and counters.
These graphic elements are connected with each other by horizontal and vertical connections.
Each network has at most : 5 lines of 8 columns
A network is identified by its action (only one action per network!).
A comment can be associated with the network.