Essentials of PL/I by Seymour Pollack and Theodor Sterling offers a thorough exploration of the PL/I programming language, detailing its robust features like syntax, data types, control structures, and advanced capabilities such as multitasking and exception handling. The book is designed to equip both new and seasoned programmers with the skills to harness PL/I's power. Although PL/I's widespread use has waned, it continues to play a crucial role in high-stakes environments—such as maintaining legacy systems in major financial institutions and government agencies where the language's reliability and precision are indispensable. PL/I also thrives in specialized applications within high-performance computing and remains a fascinating subject of study for those interested in the evolution of programming languages. Through this book, readers gain the tools to master a language that still powers critical systems and preserves the technological heritage of the modern age.