Programming:

Programming Language:

Ladder logic (LAD) is one programming language used with
PLCs. Ladder logic incorporates programming functions that are
graphically displayed to resemble symbols used in hard-wired
control diagrams.
While ladder logic programs are still the most common, there are many
other ways to program PLCs. Two other common examples are
statement list and function block diagrams.

Statement list (STL) instructions include an operation and an
operand. The operation to be performed is shown on the left.
The operand, the item to be operated on, is shown on the right.

Function block diagrams (FBD) include rectangular functions
with inputs shown on the left side of the rectangle and outputs
shown on the right side.