The input/output diagram provides an overview of incoming and outgoing data and information carriers. In this model, only one symbol may be placed in each diagram grid, that is, in a field separated by lines from other fields. The top row contains data or information carriers created by a particular function (output). The left column provides symbols for incoming data or information of a particular function (input). If a function requires multiple input and/or output symbols, these will be created as occurrence copies.

In the input/output diagram, the invisible (implicit) provides input for or creates output to relationships are created automatically during the creation of functions and storage medium or information carrier symbols.

In the figure below find a simple example of an input/output diagram.