IBM Mainframe Tutorial

As exemplified by the DoD MRP II example above, COBOL applications are often very large. Many COBOL applications consist of more than 1,000,000 lines of code - with 6,000,000+ line applications not considered unusually large in many shops.

COBOL applications are also very long-lived. The huge investment in creating a software application consisting of some millions of lines of COBOL code means that the application cannot simply be discarded when some new programming language or technology appears. As a consequence business applications between 10 and 30 years-old are common. This accounts for the predominance of COBOL programs in the year 2000 problem (12,000,000 COBOL applications vs 375,000 C and C++ applications in the US alone - [Capers Jones]). Twenty years ago when programmers were writing these applications they just didn't anticipate that they would last into this millennium.

COBOL applications often run in critical areas of business. For instance, over 95% of finance–insurance data is processed with COBOL [In Cobol’s Defense]. The serious financial and legal consequences that can result from an application failure is one reason for the near panic over the year 2000 problem.

COBOL applications often deal with enormous volumes of data. Single production files and databases measured in terabytes are not uncommon.