Understanding Identifiers and Keywords in C Programming

 

Understanding Identifiers and Keywords in C Programming

The Essential Building Blocks of C Language

Programming is like learning a new language, and just like any language, it has its own grammar and vocabulary. In C programming, two very basic yet super important terms you must know are Identifiers and Keywords.

Introduction to C Language Components

When you write a program in C, you use many names, words, and symbols to make your instructions work. Among them, identifiers and keywords are two of the most used elements in every C program.

Let's understand them one by one in a very simple and friendly way.

What are Identifiers?

Meaning and Purpose

An identifier is simply the name you give to elements in your program. You can think of it like naming a pet or saving a contact in your phone. In programming, you name things like variables, functions, arrays, etc.

How Identifiers are Used

Here's how you use identifiers in code:

int number;
float height;

In this example:

• int and float are keywords

• number and height are identifiers

These are names that you choose, based on what you want your program to do.

Rules for Naming Identifiers

You can't just type anything and expect the program to understand it. There are certain rules you must follow.

Allowed Characters

• Letters (A-Z, a-z)

• Digits (0-9)

• Underscore (_) symbol

Naming Conventions

• First character: letter or underscore

• Cannot start with digit

• No symbols (@, $, %)

• Case-sensitive (Age ≠ age)

Valid Identifiers

• name

• age1

• _total

• numberOfStudents

Invalid Identifiers

• 2total (starts with number)

• total$marks (special character)

• float (reserved keyword)

What are Keywords in C?

Role of Keywords

Keywords are special words that are already reserved by the C language. You cannot use them as names for variables or functions. These words have special meaning to the compiler.

Common Keywords

Keyword	Meaning
int	Declare integer variables
float	Declare floating point variables
char	Declare character type variables
if	Condition checking
else	Alternative to if
while	Create a loop
return	Exit from a function
void	Declare no return type

There are 32 standard keywords in C. You don't need to memorize them all at once—just get familiar with the ones you use.

Difference Between Keywords and Identifiers

Feature	Keywords	Identifiers
Who defines it?	Defined by C	Defined by programmer
Can you change it?	No	Yes
Usage	Special purpose	Names for variables/functions
Example	int, return	num, marks, totalScore

Keywords are like the fixed grammar of C, while identifiers are your own custom names.

Real-Life Examples in C Code

#include <stdio.h>

int main() {
    int marks = 95;
    printf("Marks: %d", marks);
    return 0;
}

In this example:

• Keywords: int, return

• Identifiers: marks, main

Why Following Rules is Important

If you don't follow the rules, your program won't work. It's like trying to call someone using an invalid phone number. The system won't recognize it.

Common Errors Beginners Make

• Using spaces in identifiers (student name)

• Starting with a digit (1name)

• Using keyword as identifier (int int = 10;)

• Using symbols ($, @, #) in names

All of these will result in a compile-time error.

Tips to Remember Keywords and Identifiers

• Think of keywords as "reserved seats"

• Identifiers are your custom labels

• Use meaningful names (totalPrice instead of tp)

• Avoid clever names - keep them simple and clear

Summary

To sum it all up:

• Identifiers are names for elements like variables and functions

• Keywords are special reserved words with fixed meanings

• Never use keywords as identifiers

• Follow naming rules to avoid errors

Once you master these concepts, programming becomes easier and more fun!

FAQs

Q1. What is an identifier in C?

An identifier is the name you give to variables, functions, arrays, etc., in your C program.

Q2. Can I use numbers in identifiers?

Yes, but the identifier cannot start with a number. For example, marks1 is valid, but 1marks is not.

Q3. What are keywords in C?

Keywords are reserved words in C that have special meanings like int, float, if, and return.

Q4. Is C case-sensitive for identifiers?

Yes, C is case-sensitive. Total and total would be treated as two different identifiers.

Q5. Can I use while as a variable name?

No, you can't. while is a keyword in C and cannot be used as an identifier.