z/OS
z/OS is a 64-bit mainframe operating system developed by IBM, designed for enterprise-level computing with a focus on reliability, availability, and security. It is the primary operating system for IBM Z mainframe hardware, supporting high-volume transaction processing, large-scale databases, and mission-critical applications. z/OS provides a robust environment for legacy systems while integrating modern technologies like Java, Linux, and web services.
Developers should learn z/OS when working in industries such as banking, insurance, healthcare, or government that rely on mainframes for core business operations due to their unmatched stability and performance. It is essential for maintaining and modernizing legacy applications written in languages like COBOL or PL/I, as well as for developing new applications that require high security and transaction throughput. Knowledge of z/OS is also valuable for roles involving system programming, batch processing, or integrating mainframe systems with cloud and distributed environments.