Foobar


The terms foobar, or foo and others are used as metasyntactic variables and placeholder names in computer programming or computer-related documentation. They have been used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept.

History and etymology

The etymology of foobar is derived from the military slang from the World War II era FUBAR, which was bowdlerised to foobar. The word foo on its own was used earlier. Between about 1930 and 1952 it appeared in the comic Smokey Stover by Bill Holman, who stated that, he used the word due to having seen it on the bottom of a jade Chinese figurine in San Francisco Chinatown, purportedly signifying "good luck". If true this is related to the Chinese word fu, which can mean happiness or blessing.
The first known use of the terms in print in a programming context appears in a 1965 edition of MIT's Tech Engineering News. Foobar may have come about as a result of the pre-existing "Foo" being conjoined with "bar", an addition borrowed from the military's FUBAR. The use of foo in a programming context is generally credited to the Tech Model Railroad Club of MIT from circa 1960. In the complex model system, there were scram switches located at numerous places around the room that could be thrown if something undesirable was about to occur, such as a train going full-bore at an obstruction. Another feature of the system was a digital clock on the dispatch board. When someone hit a scram switch, the clock stopped and the display was replaced with the word "FOO"; at TMRC the scram switches are, therefore, called "Foo switches". Because of this, an entry in the 1959 Dictionary of the TMRC Language went something like this: "FOO: The first syllable of the misquoted sacred chant phrase 'foo mane padme hum.' Our first obligation is to keep the foo counters turning." One book describing the MIT train room describes two buttons by the door labeled "foo" and "bar". These were general purpose buttons and were often re-purposed for whatever fun idea the MIT hackers had at the time, hence the adoption of foo and bar as general purpose variable names. An entry in the Abridged Dictionary of the TMRC Language states:
The shift from the military expression FUBAR to foobar may also have been driven by the latter being a computer science pun. Since overbars designate repeating decimal numbers, the word foobar also signifies a number in hexadecimal, a base typically used in low level programming. That number is 0.F00F00F00..., which equals the decimal fraction 256/273.
The term foobar was propagated through computer science circles in the 1960s and early 1970s by system manuals from Digital Equipment Corporation. Foobar was also used as a variable name in the Fortran code of Colossal Cave Adventure. The variable FOOBAR was used to contain the player's progress in saying the magic phrase "Fee Fie Foe Foo". Intel also used the term foo in their programming documentation in 1978.

Example use in code

In this Hello World code sample in C, foo and bar are used to illustrate string concatenation:

  1. include
int main
In this Scheme code sample, foobar is used to illustrate the name of a function:
))

Examples in language