This authoritative guide to JCL has sold over 200,000 copies. The fourth edition has been revised and updated to reflect the recent changes in the language and its emerging applications, including mission-critical coverage of the two most talked about topics in the field, Year 2000 retrofitting of legacy systems and secure e-commerce. Reformatted to match the profiles of today's programmers, this edition places new emphasis on providing guidance for programmers with a PC background. JCL features no longer supported by IBM have been gathered in one chapter on obsolete technology for use by those maintaining legacy systems. The book also features updates for the latest version of OS/390, including changes in architecture, hardware, devices, and terminology.