COBOL

Yes. COBOL still processes a large share of banking, insurance, and government transactions worldwide, running on mainframes that handle high-volume batch and transaction workloads IBM's own z/OS platform is built for.

COBOL stands for Common Business-Oriented Language. It was designed in 1959 specifically for business data processing, not general-purpose or scientific computing.

COBOL's syntax is deliberately English-like and easier to read than most languages. The hard part is usually the surrounding mainframe environment (JCL, VSAM, CICS), not the language itself.

File status 35 (file not found) and abend S0C7 (data exception from invalid numeric data) are the two most frequently reported COBOL problems in production.

COBOL's new-project adoption has been flat for decades, but its existing footprint is not shrinking meaningfully. The real risk is workforce, not the language being retired.

Yes. GnuCOBOL is a free, open-source COBOL compiler that produces native executables and runs on Linux, macOS, Windows, BSD, and most Unix variants, not just IBM z/OS. It's commonly used for training, testing, and even some production workloads that don't need mainframe-specific features like CICS or VSAM.

JCL (Job Control Language) is the batch scripting language z/OS uses to run programs, allocate datasets, and chain job steps together; a COBOL program on a mainframe almost always gets invoked through a JCL job rather than run directly. Most COBOL maintenance work eventually touches JCL, so shops treat it as a companion skill rather than optional.

A copybook is a separate file holding a reusable data layout, most often a record structure, that multiple COBOL programs pull in with a COPY statement instead of retyping the same field definitions everywhere. It's COBOL's version of a shared header file, and mismatched copybooks between programs are a common source of subtle data corruption.

As of the COBOL 2002 standard, yes: it added classes, objects, methods, and inheritance on top of the traditional procedural syntax. In practice, most production COBOL predates that standard and is written procedurally, so object-oriented COBOL shows up far more in newer code than in the decades-old batch programs still running most mainframe workloads.

Windowing was a common Y2K shortcut: instead of expanding a two-digit year field to four digits, programmers added logic that guessed the century based on a threshold value, or pivot year, chosen per program. That guess only holds until the real calendar crosses the chosen pivot, so some windowed COBOL code is already producing wrong-century dates today, decades after Y2K itself, in programs nobody has re-audited since.

It adds up fast even without a full modernization project. The U.S. Government Accountability Office found that just 10 of the federal government's most critical legacy IT systems, some COBOL-based, ranging from 8 to 51 years old, collectively cost about $337 million a year to operate and maintain, and federal agencies overall put roughly 80% of their IT budgets toward operating and maintaining existing systems rather than building new ones.