Garbage In Garbage Out or GIGO is popular computing slang for “if you input the wrong data, the results will also be wrong.” The term arose in the programming community, where instructors remind students that they must check and re-check their data and coding to ensure that the results are valid, as computers will happily process wrong information and return a result. The term is also used in other industries, most notably in the recording industry, where people stress the need for good equipment, pointing out that a poor initial recording will result in an album of low quality.

George Fuechsel, and early IBM programmer, is generally credited with coining the term. He reminded students that computers will process any kind of information they are given without judgment or an eye for accuracy, and if a small mistake is made, it can result in Garbage In Garbage Out, creating a false result. As long as people are aware of the fallibility of computers, Garbage In Garbage Out isn't a huge issue, although it can be frustrating on a major project, but it does become a problem when people accept information on faith because it came from a computer.

When this happens, it is sometimes jokingly called Garbage In Gospel Out. Many computer users are guilty of assuming that computers are infallible and will always return correct results, and this can cause serious problems. On a minor level, someone could simply have incorrect facts about a situation; on a major level, someone could base a serious decision on erroneous information.

Programmers try to be aware of the Garbage In Garbage Out principle, and in fact many computers have the capacity to check code for basic errors in an attempt to correct obvious problems in data before it is entered. Most input data, however, still needs to be proofread, especially if it is complex and filled with multiple arguments, as is common in advanced computing. This is one reason scientists like to confirm data with scientists in other locations, to ensure that their calculations are correct.

The principle of Garbage In Garbage Out can apply to lots of other things in your life as well. For example, you may have noticed that when you cook with poor quality ingredients, the result is often disappointing as well. Likewise and on a more serious level, students who suffer from a poor education often struggle to succeed in life. The lesson behind Garbage In Garbage Out is that it pays to ensure that something is of good quality before you use it, whether it's code or a new central heating system.