Can identifiers

Because this function is a special function. If you name any variable as main , you may confuse the Compiler. In the C language identifiers are the names given to variables, constants, functions , structures , pointers , or any other user-defined data, to identify them. Because it's up to the user to define the Identifiers, hence there are some rules that one has to follow, which are defined by the C language, to avoid unnecessary errors in the compiler.

Identifiers are case-sensitive in the C language. For example, name and Name will be treated as two different identifiers. No special characters , such as a semicolon , period , whitespaces , slash , or comma are permitted to be used in or as an Identifier. Let's see a few examples where we'll use keywords and identifiers. We will define a C variable , so do not get confused, we will be learning about variables very soon.

When we declare a variable or any function in any C language program, to use it we must provide a name to it, that name is then used throughout the program, for example:. Here myvariable is the name or identifier for the variable which stores the value " Studytonight " in it.

And int is the keyword. And all of them are tokens. The C language compiler will think that we have mistakenly used two data types together and will give an error.

Because void is also a data type in the C language hence it is a keyword. The identifier is just the name given to the variable, while a variable represents a memory field where some data is stored based on its data type. It's just like what is the difference between you and your name. Your name is just a word that people call you with, while you are a human being.

This tutorial was all about keywords and identifiers in C language. They both are parts of the token. Tokens in C are defined as the smallest individual element in C and are the basic building blocks of creating a program. We have covered keywords and identifiers in detail along with their valid syntax. By convention, Microsoft uses an underscore and an uppercase letter to begin macro names and double underscores for Microsoft-specific keyword names.

To avoid any naming conflicts, always select identifier names that do not begin with one or two underscores, or names that begin with an underscore followed by an uppercase letter. The following are examples of valid identifiers that conform to either ANSI or Microsoft naming restrictions:.

Although identifiers in source files are case sensitive by default, symbols in object files are not. Microsoft C treats identifiers within a compilation unit as case sensitive. The Microsoft linker is case sensitive. You must specify all identifiers consistently according to case. The "source character set" is the set of legal characters that can appear in source files. The source character set and execution character set include the ASCII characters used as escape sequences.

See Character Constants for information about the execution character set. An identifier has "scope," which is the region of the program in which it is known, and "linkage," which determines whether the same name in another scope refers to the same identifier.

These topics are explained in Lifetime, Scope, Visibility, and Linkage. Feedback will be sent to Microsoft: By pressing the submit button, your feedback will be used to improve Microsoft products and services. Privacy policy. Ethical Hacking. Computer Graphics. Software Engineering.

Web Technology. Cyber Security. C Programming. Control System. Data Mining. Data Warehouse. Javatpoint Services JavaTpoint offers too many high quality services.

Rules for constructing C identifiers The first character of an identifier should be either an alphabet or an underscore, and then it can be followed by any of the character, digit, or underscore. It should not begin with any numerical digit. In identifiers, both uppercase and lowercase letters are distinct. Therefore, we can say that identifiers are case sensitive. Commas or blank spaces cannot be specified within an identifier.

Keywords cannot be represented as an identifier. The length of the identifiers should not be more than 31 characters. Identifiers should be written in such a way that it is meaningful, short, and easy to read. External Identifier If the identifier is used in the external linkage, then it is known as an external identifier.