Difference Between Identifier and Variable

The word ‘identifier’ clearly defines itself; an identifier is a name given to an entity, which distinctly identifies an entity in a program at the time of its execution. Variable is also an identifier; its name uniquely identifies itself in a program.

Here, the fundamental difference between an identifier and variable is that an identifier is a “name given to entity” in a program whereas, a variable is a “name given to memory location”, that is used to hold value, which may get modified during program execution.

Furthermore, the name given to a variable, function, class, structure, that is in the source code of the program is an identifier. As against, a variable is a name associated with the memory cell whose value can be altered in a program. The number of characters can be more in the identifier as compared to a variable.

Content: Identifier Vs Variable

1. Comparison Chart
2. Definition
3. Key Differences
4. Conclusion

Comparison Chart

Basis for Comparison	Identifier	Variable
Use	Identifier is used to name a variable, function, class, structure, union etc.	Variable is used to name a memory location, which holds a value.
Purpose	Created to give a unique name to an entity.	Allots a unique name to a particular memory location.
Range	All identifiers are not variable.	All variables names are identifier.
Example	int a; or int a(){ // }	int a; or float a; //

Definition of Identifier

The name we use to call a particular entity in a program, which is not a keyword is called “identifier“. Identifier particularly names a ‘variable, function, structure, enum, class etc’. An identifier distinctly identifies an entity in a program while its execution. Two identifiers cannot have the same name in a program.

Example

Let’s understand it with an example.

float area;

Here ‘float’ is a ‘keyword’, and ‘area’ is an ‘identifier’. The identifier ‘area’ is a name given to a ‘variable’ which will store a float value. Now if ‘area’ weren’t a variable, but a function, then

float area(){
}

Here, ‘area’ is still an identifier, but this time, the identifier ‘area’ is a name given to a ‘function’. We have discussed the rules for naming an identifier in our previous article difference between keyword and identifier; you can go through it to understand it in a better way.

Definition of Variable

Variable is a “name given to a distinct memory location”. This named memory location contains a value which may be modified while the program gets executed. In C, a variable must be declared at the beginning of a program whereas, in C++, a variable could be declared anywhere in a program.

Types of Variables

Variables can be ‘local’, ‘global’ or ‘reference’ .

• Local variables are declared inside a function
• Global variables are declared outside a function.
• Reference variables are those which provide an “alternate name” for the previously defined variable.

If a variable is referenced to another variable, both the variables can be used alternately to represent that variable. If a variable accepts the value of an argument in a function, these variables are called ‘formal parameter’.

Rules for creating a Variable

• It can contain any combination of the alphabets, digits or underscores.
• Some compilers permit only variable having the length up to 247 characters. However, programmers prefer to use up to 31 characters length for a variable as this is convenient for them.
• The initial character of a variable name should be an alphabet or underscore as it is an identifier some of the rules are similar.
• Use of commas and blanks is not permitted within a variable name.
• None of the special symbols except ‘underscore’ can be used in a variable name.

Declaration of a variable

//type vaiable_name;
int add;

A list of variables of the same type can be created at an instance, separated by a comma.

//type variable_list;
int a, b, c;

In C++ variables could be initialized at runtime; it is referred to as ‘dynamic initialization’.

Example

float area = 3.14*rad*rad;

This statement would initialize the variable ‘area’ at runtime.

Conclusion

As identifier and variable names are user-defined names, it should be taken care that no two identifiers or no two variable names in a program should be the same. It will create a problem of ambiguity in a program.