What Does Garbage In, Garbage Out (GIGO) Mean?
Garbage in, garbage out (GIGO), in the context of information technology, is a slang expression that means regardless of how accurate a program's logic is, the results will be incorrect if the input is invalid.
While the term is most frequently used in the context of software development, GIGO can also be used to refer to any decision-making systems where failure to make right decisions with precise, accurate data could lead to wrong, nonsensical results.
Techopedia Explains Garbage In, Garbage Out (GIGO)
A program gives inaccurate results due to inaccurate data provided because a computer will always attempt to process data given to it. Said another way, the output quality of a system usually can't be any better than than the quality of inputs.
Garbage can be data that is simply filled with errors, but it can also be data that doesn't have any applicability to the specific circumstance. For example, imagine a company that only sells to .NET developers. A CRM application might be able to determine the most likely targets from a batch of leads. However, if the leads were generated from a group of Java developers who have no interest in the product, the CRM application will produce useless results regardless of its logic.
The solution is to not just spend time on an application's algorithms, but also spend time validating the input and/or ensuring that the right sort of data goes into the system.
The term garbage in, garbage out (GIGO) is widely attributed to be coined by George Fuechsel, an IBM programmer and instructor.