COBOL
The programming language most business logic on the mainframe is written in. Verbose by design, and still running the world's payments.
Also written Common Business-Oriented Language
COBOL, or Common Business-Oriented Language, was designed in 1959 for business data processing, and that is still exactly what it does. Banking, insurance, payroll, government benefits and retail systems are largely written in it.
Its defining trait is verbosity, and it was deliberate. The language was meant to be readable by people who were not programmers, so it uses English words where other languages use symbols. Adding two numbers can be written as a sentence. The result is code that is long but unusually plain to read.
It is also built around the shape of business data. Fixed-length records, decimal arithmetic that behaves the way money should, and precise control over how each field is stored and displayed are all first-class concerns. Calculating interest without rounding errors is something COBOL does naturally and many modern languages do awkwardly.
Learning it is not the hard part. The language is small and the syntax is plain. The real work is reading an existing program of several thousand lines and understanding the business rules embedded in it.
Related terms
- COBOL divisionsThe four fixed sections every COBOL program is built from, always in the same order.
- PICTURE clauseThe COBOL declaration that says what kind of data a field holds and how long it is, written as PIC.
- CopybookA shared block of COBOL declarations kept in a library and included into programs, so a record layout is defined once.
- CompileTurning COBOL source code into machine instructions, checking the syntax and producing a listing of any errors.
- Legacy systemAn older system still doing essential work. On the mainframe, usually code that has been correct and running for decades.
- Mainframe application developerThe person who writes and changes the business programs: COBOL, JCL, SQL and the logic that runs the organisation.