By Rajiv Chandrasekaran
Washington Post Staff Writer
Sunday, August 2, 1998

A brief glossary of common terms associated with the Year 2000 glitch.

BIOS: A computer's basic input-output system. It is a program that is built into a computer's read-only memory. When a computer is turned on, the BIOS is responsible for checking various system functions. It also provides information to software applications when they are running. The BIOS collects date and time information from a PC's real-time clock, which stores only the last two digits of the year. On many older PCs, the BIOS assumes that the first two digits of the year are 1 and 9. The BIOS, in turn, provides that information – including its assumption about which century we're in – to some software applications.

Cobol: It's short for common business-oriented language, a common programming language used to develop applications on mainframe computers. It is known for its English-like readability.

Embedded chip: Microchips that are embedded in the circuitry of electronic devices. The chips perform a variety of computing-related tasks, from indicating when a unit needs maintenance to regulating temperatures. The worry is that while some chips depend on dates, they don't understand the year 2000. If not fixed, machines could go haywire; some elevators, for example, "thinking" that decades have passed since they were last serviced, could shut down.

Source code: Programming instructions originally written by a person. Many computers cannot understand raw source code. Instead they compile the code into instructions the machine can understand. Those compiled instructions are saved in the computer's memory while the source code often is jettisoned. When searching for the date glitch, however, it is easier – and often essential – for programmers to examine the original source code.

Windowing: A technique used to solve the Y2K glitch in Cobol applications. Years are still represented by two digits instead of four. Every time a date is used in a calculation, the computer checks to figure out whether it should assume the first two digits are 19 or 20. A 50-year windowing approach would work this way: If the year is from 00 to 49, the software will assume it's the next century. If it's from 50 to 99, the machine will think that a 19 goes in front.