Garbage in, garbage out

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In computer science, garbage in, garbage out (GIGO) describes the concept that flawed, or nonsense input data produces nonsense output or "garbage".

The specific phrase is accredited by FOLDOC to the late Wilf Hey, who is also accredited by FOLDOC for work in developing RPG while working at IBM in 1965.

The principle also applies more generally to all analysis and logic, in that arguments are unsound if their premises are flawed.


It was popular in the early days of computing, but applies even more today, when powerful computers can produce large amounts of erroneous data or information in a short time. The first use of the phrase has been dated to a November 10, 1957, syndicated newspaper article about US Army mathematicians and their work with early computers,[1] in which an Army Specialist named William D. Mellin explained that computers cannot think for themselves, and that "sloppily programmed" inputs inevitably lead to incorrect outputs. The underlying principle was noted by the inventor of the first programmable computing device design:

On two occasions I have been asked, "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" ... I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

— Charles Babbage, Passages from the Life of a Philosopher[2]

More recently, the Marine Accident Investigation Branch comes to a similar conclusion:

A loading computer is an effective and useful tool for the safe running of a ship. However, its output can only be as accurate as the information entered into it.

— MAIB, SAFETY FLYER Hoegh Osaka: Listing, flooding and grounding on 3 January 2015[3]

The term may have been derived from last-in, first-out (LIFO) or first-in, first-out (FIFO).[4]

"Garbage in, gospel out" is a more recent expansion of the acronym.[5] It is a sardonic comment on the tendency to put excessive trust in "computerised" data, and on the propensity for individuals to blindly accept what the computer says.[5] Since the data entered into the computer is then processed by the computer, people who do not understand the processes in question, tend to believe the data they see and take it just as seriously as if the data were Gospels:[5]

Decision-makers increasingly face computer-generated information and analyses that could be collected and analyzed in no other way. Precisely for that reason, going behind that output is out of the question, even if one has good cause to be suspicious. In short, the computer analysis becomes a credible references point although based on poor data.[6]


The term can also be used as an explanation for the poor quality of a digitized audio or video file. Although digitizing can be the first step in cleaning up a signal, it does not, by itself, improve the quality. Defects in the original analog signal will be faithfully recorded, but might be identified and removed by a subsequent step by digital signal processing.

GIGO is commonly used to describe failures in human decision-making due to faulty, incomplete, or imprecise data. This sort of issue predates the computer age, but the term can still be applied.

GIGO was the name of a Usenet gateway program to FidoNet, MAUSnet, e.a.[7]

In statistics, it is not possible to carry out an accurate statistical analysis of inaccurate data.[8]

See also[edit]


  1. ^ "Work With New Electronic 'Brains' Opens Field For Army Math Experts". The Hammond Times. p. 65. Retrieved March 20, 2016 – via
  2. ^ Babbage, Charles (1864). Passages from the Life of a Philosopher. Longman and Co. p. 67. OCLC 258982.
  3. ^ MAIB (2016-03-17). "SAFETY FLYER" (PDF). MAIB. Retrieved 2016-03-19.
  4. ^ Quinion, Michael (5 November 2005). "Garbage in, garbage out". World Wide Words. Retrieved 2012-02-26.
  5. ^ a b c Paul Watzlawick (1988). Aldri så godt at det ikke er galt for noe [Von schlechten des Guten oder Hekates Losungen] (in Norwegian). Translated by Kjell Olaf Jensen. [Oslo]: Ex Libris. p. 78. ISBN 978-8273841360.
  6. ^ Daniel T. Brooks, Brandon Becker and Jerry R. Marlatt (1981). "Computer Applications in Particular Industries: Securities". Computers & The Law, American Bar Association, Section of Science and Technology (Third ed.). pp. 250, 253.CS1 maint: uses authors parameter (link)
  7. ^ jfesler (2001-01-01). "GIGO History". Retrieved 2014-01-24.
  8. ^ "Garbage In, Garbage Out: How Anomalies Can Wreck Your Data – Heap – Mobile and Web Analytics". 7 May 2014.