What is the definition of a "variable"?

Question

The standard states that

An entity is a value, object, reference, function, enumerator, type, class member, template, template specialization, namespace, parameter pack, or this.

This implies that a "variable" is not an entity.

But further in the standard said:

Every name that denotes an entity is introduced by a declaration. Every name that denotes a label is introduced either by a goto statement (6.6.4) or a labeled-statement (6.1).

and

A variable is introduced by the declaration of a reference other than a non-static data member or of an object. The variable’s name denotes the reference or object.

I'm assume from this two quotes that a variable is a name.

It is because the variable is introduced by declaration of reference and every name that denotes entity introduced by a declaration. But what does a variable's name mean? A variable is also a name by definition.

Answer 1

I'm assume from this two quotes that a variable is a name.

No, from the quotes you provided, a variable is an object or a reference which has a name.

It is because the variable is introduced by declaration of reference and every name that denotes entity introduced by a declaration.

The declaration introduces both the variable (the object or reference), and its name. This doesn't imply that that variable is the name, just that both are introduced by the declaration.

Answer 2

The definition of the term variable is a bit ambiguous in this respect, but by looking at the various uses of the term variable in the c++ standard, it looks like a variable is a special kind of entity. It is either an object or a reference. However, not all objects or references are variables, only the ones introduced the way described in [basic]/6:

A variable is introduced by the declaration of a reference other than a non-static data member or of an object. The variable's name, if any, denotes the reference or object.

Note that some variables are unnamed, for example the parameter of the function f in the example below:

void f(int) {}

int main() {}

Answer 3

The best simple definition I can think of is: a Variable is trio of name, address and type (usually implies a size).

Originally it was meant to hold a changeable value but some languages allow this value to be constant (write once).

Answer 4

A variable is, as you say, the name of "a something". That "a something" is either a reference (to another object) or an object. Note that object here does not infer "an instance of a class", so an object could be a char, array of int, or pointer to void.

This name is held by the compiler, and when code is generated, space somewhere is allocated for the variable [1], in a register or on the stack (local variables) or in "data space" (static or global variables). This gives the variable a location, an address (note that registers don't have addresses).

[1] Variables can also be eliminated if the compiler finds that the variable isn't used [or, sometimes replaced, when for example a loop optimisation is changed from one form of loop to another]