Module Reusability
This section describes the module resusability.
The Module Reusability figure (Figure 1) shows the same canonical module (for example, one that provides delete and kill processing on character strings) reused in two different streams. This module typically is implemented as a filter, with no downstream service interface. In both cases, a tty interface is presented to the stream user process because the module is nearest the stream head.
![This diagram shows two of the same user processes using the same interface to communicate with two different streams. The first stream contains the following elements, which are connected with bidirectional arrows: same interface, canonical module, class 1 transport protocol, and LAPB driver. The second stream contains the following elements, which are connected with bidirectional arrows: same interface, canonical module, and raw TTY driver. In each stream, the elements below the a dashed line representing the same interface are in the same module.](A143C12d.jpg)