Abstract: Development of interfaces for legacy programs. A system includes a client device displaying a series of screens output from a legacy program in a terminal emulator. The system further includes a tracking module logging activity in the terminal emulator in a trail file, and an analysis module adapted to analyze the trail file and produce, based on the analysis, a REST API based upon the analysis that supports a collection of different REST API calls corresponding to the series of screens output from the legacy program. The REST API is a stateless API utilized in a stateful manner in which each REST API call of the collection of REST API calls provides direct access to a corresponding screen of the series of screens.