An IDL (Interactive Data Language) programming developer manipulates, visualizes, and analyses complex data using the IDL software. They write, test, and debug IDL codes to create algorithms for data analysis and interpretation. Their work primarily involves handling scientific or medical data, such as satellite imagery or medical imaging. They also work on creating graphical user interfaces (GUIs) for interactive data visualization. The developer needs to ensure the efficient performance of the software, solve any technical issues, and often collaborate with scientists or researchers to understand their data analysis needs.