Identifiers & Keywords in C

Identifiers in C:-

Identifiers refer to the name of a variable, function and arrays. C Identifiers are names given to different entities such as constants, variables, structures, functions, etc.

Examples :-

int amount;
double totalbalance;

In the above example, amount and totalbalance are identifiers, and int and double are keywords.

Rules for Identifiers:-

• First Character must be an alphabet (or underscore).
• must consist of only letters, digits, or underscore.
• It should be up to 31 characters long.
• Cannot use a keyword.
• must not contain white space.
• Identifier names must be unique.
• Identifiers are case-sensitive.

Types of Identifier in C:-

There are two types of Identifier in c.

1. Internal Identifier
2. External Identifier

1. Internal Identifier:- Identifiers which are used as a local variable or are not used in external linkage are called internal identifiers.

2. External identifier: Identifiers which are used as a global variable or used for naming function or any other external linkage are called external identifiers.

Keywords in C:-

Keywords are generally called as pre-defined or reserved words in a programming language. Every keyword in C language performs a specific function in a program.

Facts about Keyword :

• Keywords cannot be used as variable names.
• Keywords have fixed meanings, and that meaning cannot be changed.
• They are the building block of a ‘C’ program.
• C supports 32 keywords.
• All the keywords are written in lowercase letters.

The different types of keywords are as follows −

Examples :-

#include<stdio.h>

int main()
{
    float a, b;
    printf("Showing how keywords are used.");
    return 0;
}

In the above program, float and return are keywords. The float keyword is used to declare variables, and the return is used to return an integer type value in this program.