Metasyntaxic variable

In Data-processing programming , a metasyntaxic variable is a generic Variable, used in the examples to concentrate on the bottom rather than on the form, and whose name is selected to be tacitly recognized like such by the administrators and the programmers. The word louse is the example more speaking. The use of the metasyntaxic variables makes it possible to release the engineer of the search for a name of logical variable adequate on the studied subject.

The metasyntaxic variables are called thus because:

they are variables in the Métalangage employed to speak about the programs, etc (see also the Pseudo-code);
these are variables whose values are often variables (as in uses such as “the value of F (louse, touched) is the sum of louse and touched”).

However, a plausible suggestion is that the true reason for the term variable metasyntaxic is that sounds well. This term belongs to the computerese.

Examples

Stories of Louse

louse is the French-speaking metasyntaxic variable most current. Traditionally, the first metasyntaxic variable of a program or a function will be called louse . In answer to louse , several continuations of metasyntaxic variables are used, according to criteria as complex as the origin or the mood of the programmer.

It is supposed that the louse metasyntaxic nominates originally the same person as the recurring Toto of the funny stories.

touched , titi , tutu constitute a “logical” continuation of louse .
blop , corner , side constitutes another “logical” continuation, originating in the National university of Lyon.
totoche is rarer.
pipo starts to be spread, like pouet or pwet or trout .

Other variables used

Teleprinters

At the time of the Teleprinter S ASR33 and KSR33, of which the keyboard was very inconvenient, name KLIO (these teleprinters had only capital letters) was often used because of the proximity of these 4 keys and the facility of pronunciation of the variable.

Language FORTRAN

In FORTRAN, first scientific language of very mass use, the convenience to use variables I, J, K… (in fact, any variable whose name started with a letter of I with NR) without having to state them nor to specify that they were whole contributed to the popularity of the language: it was they whom one generally used as indices of loop. In the same way, variables X, Y, Z (and all those starting with a letter of has to H or of O with Z) were implicitly recognized like floating. The names of a letter, or a letter and a figure, were often used for local practice without incidence on the remainder of the program (of calculations of sums or products, for example).

In English

foo : historically fu , for fucked up , or perhaps forward observation officer , known during the Second world war in particular for the inscriptions left behind the enemy lines foo was young stag ; according to another interpretation, it would be about the Acronyme of File Gold Object ;
bar , continuation of foo : foobar is then the acronym of fucked up beyond all recognition/to repair ;
baz , continuation of foo and bar ;
qux , continuation of foo , bar and baz ;
fum also, but rarer.

Others

42, metasyntaxic value, response to the Life, the Universe and the Remainder
Gloubi-boulga
Asdf, beginning of the second line of a keyboard QWERTY
John Doe and Alan Smithee, names of anybody
index, idx, for the position of the cursor in a list of data
has, B, C, because certain developers prefer this with louse, plop, or foo
In Cryptographie, Alice sends to Bob a message which Estelle tries to intercept (or Oscar).

See too

Article related

False-text, an equivalent in Printing works
Intron, an equivalent in the Genome

External bond

Etymology off " Foo" , standardization of the metasyntaxic variables by IETF, April 1st, 2001.

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