Each ESL module is a set of action routines that perform commonly used actions. Modules can save you considerable programming time; instead of writing the action statements yourself, you can simply reference the appropriate module in your program.

 

For example, ESL includes standard modules to implement functionality such as communicating with host computers and generating business graphics.

 

You reference a module using the module environment declaration. This makes the action routines that make up the module available in your ESL program. You can reference any number of modules in an ESL program.

 

When you reference a module, each action statement that is part of the module is available in your program exactly as though you had specified its definition in the program. Arguments are passed to the module by storing data in variables defined by the module. Similarly, outputs from the module are stored in variables that it defines, and these variables can be referenced in your program.

 

ESL modules are stored in the module subdirectory of your main ESL directory. Each module has both a public file and a private file. The public file (which has the extension .PUB) is a quick reference on how to use the module and defines the variables that you use to pass information to and from the module's routines. The private file, which has the extension .PRI, contains the code that performs the actions.