1. [numerical analysis] Said of an algorithm or computational method that tends to blow up because of accumulated roundoff error or poor convergence properties.

2. Software that bypasses the defined operating system interfaces to do things (like screen, keyboard, and disk I/O) itself, often in a way that depends on the hardware of the machine it is running on or which is nonportable or incompatible with other pieces of software.

In the IBM PC/mess-dos world, there is a folk theorem (nearly true) to the effect that (owing to gross inadequacies and performance penalties in the OS interface) all interesting applications are ill-behaved.

See also bare metal. Opposite: well-behaved, compare PC-ism.

[Jargon File]


Assembly language for the ILLIAC computer. Listed in CACM 2(5):16, (May 1959) p.16.

Illiac IV


One of the most infamous supercomputers ever. It used early ideas on SIMD (single instruction stream, multiple data streams). The project started in 1965, it used 64 processors and a 13MHz clock. In 1976 it ran its first sucessfull application. It had 1MB memory (64x16KB).

Its actual performance was 15 MFLOPS, it was estimated in initial predictions to be 1000 MFLOPS. It totally failed as a computer, only a quarter of the fully planned machine was ever built, costs escalated from the $8 million estimated in 1966 to $31 million by 1972, and the computer took three more years of enginering before it was operational.

The only good it did was to push research forward a bit, leading way for machines such as the Thinking Machines CM-1 and CM-2.

Last updated: 1995-04-28

Illinois Functional Programming


(IFP) An interpreter written in portable C by Arch D. Robison for a variant of Backus's FP with syntax like ALGOL or Modula-2. IFP Runs under Unix, CTSS (Cray) and MS-DOS.

Version: 0.5. Posted to comp.sources.unix volume 10.

["The Illinois Functional Programming Interpreter", A.D. Robison, Proc 1987 SIGPLAN Conf on Interpreters and Interpretive Techniques (June 1987), pp. 64-73].

["Illinois Functional Programming: A Tutorial", A.D. Robison, BYTE Feb 1987, pp. 115-125].

Last updated: 1994-10-24

Nearby terms:

I-LinkILISPill-behavedILLIACIlliac IVIllinois Functional Programming

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