3.2.2 Writing a New Extension

Important Note: These instructions are only for writing a new extension that draws pictures. Currently, in Cogsys 3.0.15, the Load Extension Routine Command (%X) can only load one type of extension, a picture generator, and only one command uses the loaded extension, Create Picture from CXR, %I. This will most likely change as extensions become more powerful, but for now we assume that you are writing a picture generator.

Writing an extension isn't hard. From an "administrative" point of view, there are only three things that the extension writer must be aware of: passed arguments, main program objects, and data segments. Of course, the extension itself can be as complicated as you like it. Here we only describe the three basic requirements that are common to all extensions. Details which are specific to an extension (for example, drawing text characters) are noted briefly in the descriptions above for the individual extensions. See section Extension Reference.

We will illustrate this discussion with examples from a fictional CXR called SHAPE, which will draw circles and squares of varying sizes.

3.2.2.1 Passed Arguments
3.2.2.2 Main Program Objects
3.2.2.3 Data Segments