Identifiers

IDENTIFIERS

Identifiers, as the name suggests, help us to identify data and other objects in the program. Identifiers are basically the names given to program elements such as variables, arrays, and functions. Identifiers may consist of sequence of letters, numerals, or underscores.

Rules for Forming Identifier Names

Some rules have to be followed while forming identifier names. They are as follows:

• Identifiers cannot include any special characters or punctuation marks (like #, $, ^, ?,., etc.) except the underscore’_’

• There cannot be two successive underscores.

• Keywords cannot be used as identifiers.

• The case of alphabetic characters that form the identifier name is significant. For example, 'FIRST' is different from 'first' and 'First'.

• Identifiers must begin with a letter or an underscore. However, use of underscore as the first character must be avoided because several compiler-defined identifiers in the standard C library have underscore as their first char- acter. Hence, inadvertently dupli- cated names may cause definition conflicts.

Programming Tip: C is a case sensitive language. If you type printf function as Printf, then an error will be generated.

• Identifiers can be of any reasonable length. They should not contain more than 31 characters. They can actually be longer than 31, but the compiler looks at only the first 31 characters of the name.

Although it is a good practice to use meaningful identifier names, it is not compulsory. Good identifiers are descriptive but short. To cut short the identifier, you may use abbreviations. C allows identifiers (names) to be up to 63 characters long. If a name is longer than 63 characters, then only the first 31 characters are used.

As a general practice, if the identifier is a little long, then you may use an underscore to separate the parts of the name or you may use capital letters for each part. Examples of valid identifiers include:

roll_number, marks, name, emp_number, basic_ pay, HRA, DA, dept code, Dept Code, RollNo, EMP NO

Examples of invalid identifiers include:

23_student, %marks, @name, #emp_number, basic.pay, -HRA, (DA), &dept_code, auto

Note

C is a case-sensitive language. Therefore rno, Rno, RNo, RNO are considered as different identifiers.