Ladder editing takes place in a "matrix". Each matrix position provides a location to hold one input, output, or branch instruction. Matrix locations are divided into two types - inputs and outputs. Input matrix locations only hold input (including branch) instructions, while output matrix locations only hold output intructions.
There are three types of instruction matrices. Single input matrices are for output instructions which take one input per instruction. Double input matrices are for output instructions which take two inputs per instruction. Triple input matrices are for output instructions which take three inputs per instruction.
Instructions from different output classes cannot be mixed together in the same rung. When a new rung is created, at least one output instruction must be added to the rung before the editing matrix can be created. The class of the first instruction selected determines the type of matrix created. Once a matrix has been created, the adding of incompatible output instructions is disabled. Changing instruction classes requires clearing the rung (erasing all the existing instructions in the rung).
Most output instructions are "single input" instructions. The edit matrix allows up to 8 outputs (1 column of 8) and 64 inputs (8 columns and 8 rows) and per rung.
Several instructions are "double input" instructions. The edit matrix allows 1 output, and 16 inputs (2 rows of 8 columns). Each input row must be connected independently to the associated output branch. The input matrix locations cannot contain branch instructions.
"Triple input" instructions are similar to "double input" instructions. The edit matrix can only contain 1 output, but contains 24 inputs (3 rows of 8 columns).
Individual matrix locations can be selected by clicking on them. When a matrix location is selected, buttons appropriate to that location (input or output) are automatically displayed.