No, ISTD is not all about coding. ISTD focuses on the design, development, and application of information systems to solve real world problems. In ISTD, you learn algorithms, techniques to secure complex systems, methods for reliable data communications, algorithms for machine learning, analysis of algorithms, logic for Artificial Intelligence, and many more. Learning these often does require the design of computer programs, but is more so as a means to an end. It is by no means the main focus of what you learn in ISTD.