GIGO (garbage in, garbage out) – definition

GIGO stands for garbage in, garbage out. It is a computer science and mathematics concept that the quality of the input determines the quality of the output. In other words, in a processing system, the data’s quality coming out cannot be better than what went in.

Therefore, a program will only yield misleading results if it is working on faulty data.

In mathematics, for example, if somebody states an equation improperly, the answer will probably be incorrect.

Computers can only operate on strict logic. Therefore, invalid input may result in ‘garbage’ or unrecognizable output. If I try, for example, to open a binary file in a text editor, it will probably display unreadable content.

‘Garbage’ in this context means rubbish, trash, nonsense, or faulty. says the following regarding GIGO:

“Stands for ‘Garbage In, Garbage Out.’ GIGO is a computer science acronym that implies bad input will result in bad output.” also explains that GIGO is a universal computer science concept. However, it applies only to programs that process faulty or invalid data.

Good programming will avoid producing garbage because it will not accept faulty data in the first place.

We pronounce the term ‘GIGO’ ‘guy-go’ and not ‘gih-go.’

GIGO garbage in garbage out - definition and illustration
Don’t blame the computer if its output is faulty. Output is only as good as input. In other words, the information the computer gives out is only as good as the information that went in. IT stands for Information Technology (computers).

GIGO – short history

The term GIGO was popular in the early years of computing. However, today, when computers can produce huge amounts of bad data in a short time, it applies even more.

In 1957, a syndicated newspaper article about US Army mathematics first used the term. In the article, an Army Specialist, William Mellin, wrote that computers cannot think for themselves. Therefore, ‘sloppily programmed’ inputs lead to faulty outputs.

Charles Babbage (1791-1871), who invented the first programmable computing device design, once said regarding faulty input:

“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.”

We use the term GIGO when talking about the poor quality of a digitized video or audio file. We also use it to describe failures in people’s decision-making due to imprecise or incomplete data.

Video – GIGO

This UK Industrial Film looks at computers and how we perceived them in 1969. It begins with somebody asking people what they thought of computers. Even then, people were aware of faulty data in computers.